👤 M John Chapman

Neuritin 1 (NRN1) has emerged as a multifaceted regulator of synaptic plasticity, neuronal excitability and structural remodelling. This review synthesises knowledge of NRN1 function across the central and peripheral nervous systems, with a focus on its roles in sensory neurones and neuronal repair following injury. We discuss evidence that NRN1 interacts with classical neurotrophic pathways, including brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF), while engaging distinct cellular mechanisms that span activity-dependent trafficking, modulation of calcium and potassium channel function and regulated local axonal mRNA translation. Accumulating data indicate that NRN1 contributes to injury-induced plasticity and functional recovery through both cell-autonomous neuronal mechanisms and non-cell-autonomous signalling involving glial and stromal cells. In long-projecting sensory axons, regulated transport and local translation of Nrn1 mRNA position NRN1 as a spatially restricted effector of axonal growth, excitability and regeneration. Dysregulation of NRN1 expression and signalling has been implicated in pathological contexts including neurodegeneration, diabetic peripheral neuropathy and inflammatory pain, where restoration of NRN1 activity promotes axonal integrity, Schwann cell survival and neurotrophic support. Beyond neurons, NRN1 also modulates inflammatory and angiogenic pathways, including VEGF and CXCR4 signalling, linking neuronal plasticity to broader tissue and immune responses. Together, these findings support a model in which NRN1 acts as a molecular integrator of neurotrophic, metabolic and injury-associated signals, coordinating plasticity while also presenting potential routes to maladaptive sensitisation. We highlight key mechanistic and translational challenges that must be addressed to harness NRN1 biology therapeutically aimed at enhancing neuronal repair while limiting persistent sensory dysfunction. Show less

Physical activity (PA), sedentary behavior (SB), and sleep independently influence cardiometabolic health in youth. Because these behaviors are interdependent within a 24-hour day, compositional data analysis has emerged as a method to examine how the distribution of time across behaviors relates to health. While evidence exists for adults and preschool-aged children, findings for school-aged youth, who are at higher risk for inactivity, remain limited. This systematic review examined associations between light PA (LPA), moderate-to-vigorous PA (MVPA), SB, and sleep and cardiometabolic health among youth aged 6 to 17 years. In May 2024, two reviewers conducted systematic searches across five databases following Cochrane criteria. Eligible studies were peer reviewed, included youth aged 6 to 17 years, and used compositional data analysis to assess cardiometabolic outcomes. Of 1,021 records screened, 10 studies met inclusion criteria, and 9 were rated moderate or high quality. MVPA, particularly vigorous PA, showed the most consistent benefits, including lower adiposity, reduced cardiometabolic risk, and higher fitness. SB was generally associated with adverse outcomes, while findings for LPA and sleep were mixed or null. Overall, evidence suggests that daily movement behavior distributions are important predictors of cardiometabolic health in youth and support movement-based public health guidance. Show less

Apolipoprotein B-containing triglyceride-rich lipoproteins (TRLs) -chylomicrons, very low-density lipoproteins (VLDL), their remnants, and intermediate-density lipoproteins (IDL) - are recognised as key contributors to atherosclerotic cardiovascular disease (ASCVD). On a per particle basis, genetic and clinical evidence indicates that TRL/remnants exhibit a greater atherogenic potential than LDL and evidence points to this being mediated by enhanced arterial wall retention of TRLs, the pro-inflammatory actions of their constituent apolipoproteins and cargo of cholesterol and bioactive lipids, and their capacity to induce endothelial dysfunction. Despite the strong association between plasma triglyceride levels and ASCVD, TRL-lowering trials have produced inconsistent, often negative results. The answer to this conundrum, as explored here, likely lies in the complexity of TRL structure, composition and metabolism, and in the dynamic influence that TRLs have on the properties of LDL, the most abundant atherogenic lipoprotein. The substantial heterogeneity in the TRL/remnant/IDL spectrum means that these particles present a wide range of potentially pathogenic factors to the artery wall in the form of major and minor lipids and a variety of surface apolipoproteins. Significant gaps exist in our knowledge: how are TRL remodelled during their lifetime in the bloodstream to become cholesterol-enriched lipoproteins; which are the most relevant TRL subspecies or TRL constituents, that initiate and progress the formation of atherosclerotic lesions; and what are the prime targets for effective intervention. Critical to the design of future triglyceride-lowering prevention trials will be the development of superior biomarkers of TRL/remnant atherogenicity and the development of a precision medicine approach to ASCVD prevention. Show less

The Helix Research Network program is a large population genomics initiative that screens an all-comers population of patients for Centers for Disease Control and Prevention Tier 1 genetic conditions, including familial hypercholesterolemia (FH). We evaluated changes in clinical management and low-density lipoprotein cholesterol (LDL-C) levels among patients we identified to have FH. Participants across 9 US health systems provided samples that underwent clinical-grade exome sequencing. Individuals with a positive screening result for a Tier 1 condition were offered no-cost genetic counseling through their health system. Using medication and laboratory testing records, we evaluated changes in patients' lipid-lowering therapies and LDL-C levels. Among 228 602 adults enrolled between 2017 to 2025, 1155 (≈1/198) had a pathogenic FH variant in Following genetic screening, many patients with a pathogenic FH variant experienced improvements in clinical management and LDL-C levels. Electronic health record documentation of the diagnosis code was associated with a greater likelihood of therapeutic modifications, which, in turn, were associated with larger LDL-C reductions. Findings underscore the powerful potential of population genomic screening for supporting optimal lipid management in individuals with FH. Show less

Computer vision is increasingly used in farmers' fields and agricultural experiments to quantify important traits. Imaging setups with a sub-millimeter ground sampling distance enable the detection and tracking of plant features, including size, shape, and colour. Although today's AI-driven foundation models segment almost any object in an image, they still fail for complex plant canopies. To improve model performance, the global wheat dataset consortium assembled a diverse set of images from experiments around the globe. After the head detection dataset (GWHD), the new dataset targets a full semantic segmentation (GWFSS) of organs (leaves, stems and spikes) covering all developmental stages. Images were collected by 11 institutions using a wide range of imaging setups. Two datasets are provided: i) a set of 1096 diverse images in which all organs were labelled at the pixel level, and (ii) a dataset of 52,078 images without annotations available for additional training. The labelled set was used to train segmentation models based on DeepLabV3Plus and Segformer. Our Segformer model performed slightly better than DeepLabV3Plus with a mIOU for leaves and spikes of ca. 90 ​%. However, the precision for stems with 54 ​% was rather lower. The major advantages over published models are: i) the exclusion of weeds from the wheat canopy, ii) the detection of all wheat features including necrotic and senescent tissues and its separation from crop residues. This facilitates further development in classifying healthy vs. unhealthy tissue to address the increasing need for accurate quantification of senescence and diseases in wheat canopies. Show less

Familial chylomicronemia syndrome (FCS) is a rare autosomal recessive metabolic disorder that causes extremely elevated plasma triglyceride levels, with limited therapeutic options. Volanesorsen is an antisense oligonucleotide approved for its treatment. A 24-year-old woman with genetically diagnosed FCS secondary to a pathogenic variant in Show less

Coordinated programs of gene expression drive brain development. It is unclear which transcriptional programs, in which cell-types, are affected in neuropsychiatric disorders such as schizophrenia. Here we integrate human genetics with transcriptomic data from differentiation of human embryonic stem cells into cortical excitatory neurons. We identify transcriptional programs expressed during early neurogenesis in vitro and in human foetal cortex that are down-regulated in DLG2 Show less

In adult males, spermatogonia maintain lifelong spermatozoa production for oocyte fertilization. To understand spermatogonial metabolism we compared gene profiles in rat spermatogonia to publicly available mouse, monkey, and human spermatogonial gene profiles. Interestingly, rat spermatogonia expressed metabolic control factors Show less

Primary cilia are lost during cancer development, but the mechanism regulating cilia degeneration is not determined. While transcription factor nuclear factor-erythroid 2-like 2 (NRF2) protects cells from oxidative, proteotoxic, and metabolic stress in normal cells, hyperactivation of NRF2 is oncogenic, although the detailed molecular mechanisms by which uncontrolled NRF2 activation promotes cancer progression remain unclear. Here, we report that NRF2 suppresses hedgehog (Hh) signaling through Patched 1 (PTCH1) and primary ciliogenesis via p62/sequestosome 1 (SQSTM1). PTCH1, a negative regulator of Hh signaling, is an NRF2 target gene, and as such, hyperactivation of NRF2 impairs Hh signaling. NRF2 also suppresses primary cilia formation through p62-dependent inclusion body formation and blockage of Bardet-Biedl syndrome 4 (BBS4) entrance into cilia. Simultaneous ablation of PTCH1 and p62 completely abolishes NRF2-mediated inhibition of both primary ciliogenesis and Hh signaling. Our findings reveal a previously unidentified role of NRF2 in controlling a cellular organelle, the primary cilium, and its associated Hh signaling pathway and also uncover a mechanism by which NRF2 hyperactivation promotes tumor progression via primary cilia degeneration and aberrant Hh signaling. A better understanding of the crosstalk between NRF2 and primary cilia/Hh signaling could not only open new avenues for cancer therapeutic discovery but could also have significant implications regarding pathologies other than cancer, including developmental disorders, in which improper primary ciliogenesis and Hh signaling play a major role. Show less

Patients with methylmalonic acidemia (MMA) and propionic acidemia (PA) and urea cycle disorders (UCD), treated with a protein restricted diet, are prone to growth failure. To obtain optimal growth and thereby efficacious protein incorporation, a diet containing the essential and functional amino acids for growth is necessary. Optimal growth will result in improved protein tolerance and possibly a decrease in the number of decompensations. It thus needs to be determined if amino acid deficiencies are associated with the growth retardation in these patient groups. We studied the correlations between plasma L-arginine levels, plasma branched chain amino acids (BCAA: L-isoleucine, L-leucine and L-valine) levels (amino acids known to influence growth), and height in MMA/PA and UCD patients. We analyzed data from longitudinal visits made in stable metabolic periods by patients registered at the European Registry and Network for Intoxication Type Metabolic Diseases (E-IMD, Chafea no. 2010 12 01). In total, 263 MMA/PA and 311 UCD patients were included, all aged below 18 years of age. In patients with MMA and PA, height z-score was positively associated with patients' natural-protein-to-energy prescription ratio and their plasma L-valine and L-arginine levels, while negatively associated with the amount of synthetic protein prescription and their age at visit. In all UCDs combined, height z-score was positively associated with the natural-protein-to-energy prescription ratio. In those with carbamylphosphate synthetase 1 deficiency (CPS1-D), those with male ornithine transcarbamylase deficiency (OTC-D), and those in the hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome subgroup, height z-score was positively associated with patients' plasma L-leucine levels. In those with argininosuccinate synthetase deficiency (ASS-D) and argininosuccinate lyase deficiency (ASL-D), height was positively associated with patients' plasma L-valine levels. Plasma L-arginine and L-valine levels in MMA/PA patients and plasma L-leucine and L-valine levels in UCD patients, as well as the protein-to-energy prescription ratio in both groups were positively associated with height. Optimization of these plasma amino acid levels is essential to support normal growth and increase protein tolerance in these disorders. Consequently this could improve the protein-to-energy intake ratio. Show less

Organic acidurias (OAD) and urea-cycle disorders (UCD) are rare inherited disorders affecting amino acid and protein metabolism. As dietary practice varies widely, we assessed their long-term prescribed dietary treatment against published guideline and studied plasma amino acids levels. We analyzed data from the first visit recorded in the European registry and network for intoxication type metabolic diseases (E-IMD, Chafea no. 2010 12 01). In total, 271 methylmalonic aciduria (MMA) and propionic aciduria (PA) and 361 UCD patients were included. Median natural protein prescription was consistent with the recommended daily allowance (RDA), plasma L-valine (57%), and L-isoleucine (55%) levels in MMA and PA lay below reference ranges. Plasma levels were particularly low in patients who received amino acid mixtures (AAMs-OAD) and L-isoleucine:L-leucine:L-valine (BCAA) ratio was 1.0:3.0:3.2. In UCD patients, plasma L-valine, L-isoleucine, and L-leucine levels lay below reference ranges in 18%, 30%, and 31%, respectively. In symptomatic UCD patients who received AAM-UCD, the median natural protein prescription lay below RDA, while their L-valine and L-isoleucine levels and plasma BCAA ratios were comparable to those in patients who did not receive AAM-UCD. Notably, in patients with ornithine transcarbamylase syndrome (OTC-D), carbamylphosphate synthetase 1 syndrome (CPS1-D) and hyperammonemia-hyperornithinemia-homocitrullinemia (HHH) syndrome selective L-citrulline supplementation resulted in higher plasma L-arginine levels than selective L-arginine supplementation. In conclusion, while MMA and PA patients who received AAMs-OAD had very low BCAA levels and disturbed plasma BCAA ratios, AAMs-UCD seemed to help UCD patients obtain normal BCAA levels. In patients with OTC-D, CPS1-D, and HHH syndrome, selective L-citrulline seemed preferable to selective L-arginine supplementation. Show less

Apolipoprotein B-containing lipoproteins and low-density lipoprotein play a key role in atherosclerotic vascular disease. Modified forms of low-density lipoprotein drive inflammation, an integral aspect of plaque progression. High-density lipoprotein particles are equipped to protect low-density lipoprotein from enzymatic and nonenzymatic modification. Under normal conditions, high-density lipoproteins facilitate cholesterol efflux from tissues, preventing its accumulation with deleterious consequences. However, the high-density lipoprotein particles characteristic of dyslipidemic states associated with premature atherosclerosis are typically dysfunctional as a result of alteration in their metabolism and consequently their structure and composition. Such an effect indirectly enhances low-density lipoprotein atherogenicity. Show less

Statins impact the metabolism, concentrations, composition, and function of circulating lipoproteins. We evaluated time course relationships between statin-mediated reduction in atherogenic apolipoprotein B (ApoB)-containing particles and dynamic intravascular remodeling of ApoAI-containing lipoprotein subpopulations in the mixed dyslipidemia of metabolic syndrome. Insulin-resistant, hypertriglyceridemic, hypercholesterolemic, obese males (n = 12) were treated with pitavastatin (4 mg/d) and response evaluated at 6, 42, and 180 days. Reduction in low-density lipoprotein (LDL) cholesterol, ApoB, and triglycerides (TGs) was essentially complete at 42 days (-38%, -32%, and -35%, respectively); rapid reduction equally occurred in remnant cholesterol, ApoCII, CIII, and E levels (day 6; -35%, -50%, -23%, and -26%, respectively). Small dense LDLs (LDL4 and LDL5 subpopulations) predominated at baseline and were markedly reduced on treatment (-29% vs total LDL mass). Cholesteryl ester (CE) transfer protein activity and mass decreased progressively (-18% and -16%, respectively); concomitantly, TG depletion (up to -49%) and CE enrichment occurred in all high-density lipoprotein (HDL) particle subpopulations with normalization of CE/TG mass ratio at 180 days. ApoAI was redistributed from LpAI to LpAI:AII particles in HDL2a and HDL3a subpopulations; ApoCIII was preferentially depleted from LpAI:AII-rich particles on treatment. Overall, statin action exhibits duality in mixed dyslipidemia, as CE transfer protein-mediated normalization of the HDL CE/TG core lags markedly behind subacute reduction in elevated levels of atherogenic ApoB-containing lipoproteins. Normalization of the HDL neutral lipid core is consistent with enhanced atheroprotective function. The HDL CE/TG ratio constitutes a metabolomic marker of perturbed HDL metabolism in insulin-resistant states, equally allowing monitoring of statin impact on HDL metabolism, structure, and function. Show less

Some cholesteryl ester transfer protein (CETP) inhibitors lower low-density lipoprotein cholesterol (LDL-C) levels without reducing cardiovascular events, suggesting that the clinical benefit of lowering LDL-C may depend on how LDL-C is lowered. To estimate the association between changes in levels of LDL-C (and other lipoproteins) and the risk of cardiovascular events related to variants in the CETP gene, both alone and in combination with variants in the 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) gene. Mendelian randomization analyses evaluating the association between CETP and HMGCR scores, changes in lipid and lipoprotein levels, and the risk of cardiovascular events involving 102 837 participants from 14 cohort or case-control studies conducted in North America or the United Kingdom between 1948 and 2012. The associations with cardiovascular events were externally validated in 189 539 participants from 48 studies conducted between 2011 and 2015. Differences in mean high-density lipoprotein cholesterol (HDL-C), LDL-C, and apolipoprotein B (apoB) levels in participants with CETP scores at or above vs below the median. Odds ratio (OR) for major cardiovascular events. The primary analysis included 102 837 participants (mean age, 59.9 years; 58% women) who experienced 13 821 major cardiovascular events. The validation analyses included 189 539 participants (mean age, 58.5 years; 39% women) with 62 240 cases of coronary heart disease (CHD). Considered alone, the CETP score was associated with higher levels of HDL-C, lower LDL-C, concordantly lower apoB, and a corresponding lower risk of major vascular events (OR, 0.946 [95% CI, 0.921-0.972]) that was similar in magnitude to the association between the HMGCR score and risk of major cardiovascular events per unit change in levels of LDL-C (and apoB). When combined with the HMGCR score, the CETP score was associated with the same reduction in LDL-C levels but an attenuated reduction in apoB levels and a corresponding attenuated nonsignificant risk of major cardiovascular events (OR, 0.985 [95% CI, 0.955-1.015]). In external validation analyses, a genetic score consisting of variants with naturally occurring discordance between levels of LDL-C and apoB was associated with a similar risk of CHD per unit change in apoB level (OR, 0.782 [95% CI, 0.720-0.845] vs 0.793 [95% CI, 0.774-0.812]; P = .79 for difference), but a significantly attenuated risk of CHD per unit change in LDL-C level (OR, 0.916 [95% CI, 0.890-0.943] vs 0.831 [95% CI, 0.816-0.847]; P < .001) compared with a genetic score associated with concordant changes in levels of LDL-C and apoB. Combined exposure to variants in the genes that encode the targets of CETP inhibitors and statins was associated with discordant reductions in LDL-C and apoB levels and a corresponding risk of cardiovascular events that was proportional to the attenuated reduction in apoB but significantly less than expected per unit change in LDL-C. The clinical benefit of lowering LDL-C levels may therefore depend on the corresponding reduction in apoB-containing lipoprotein particles. Show less

Deviations from normal body weight are observed prior to and after the onset of Alzheimer's disease (AD). Midlife obesity confers increased AD risk in later life, whereas late-life obesity is associated with decreased AD risk. The role of underweight and weight loss for AD risk is controversial. Based on the hypothesis of shared genetic variants for both obesity and AD, we analyzed the variants identified for AD or obesity from genome-wide association meta-analyses of the GERAD (AD, cases = 6,688, controls = 13,685) and GIANT (body mass index [BMI] as measure of obesity, n = 123,865) consortia. Our cross-disorder analysis of genome-wide significant 39 obesity SNPs and 23 AD SNPs in these two large data sets revealed that: (1) The AD SNP rs10838725 (pAD  = 1.1 × 10(-08)) at the locus CELF1 is also genome-wide significant for obesity (pBMI  = 7.35 × 10(-09) ). (2) Four additional AD risk SNPs were nominally associated with obesity (rs17125944 at FERMT2, pBMI  = 4.03 × 10(-05), pBMI corr  = 2.50 × 10(-03) ; rs3851179 at PICALM; pBMI  = 0.002, rs2075650 at TOMM40/APOE, pBMI  = 0.024, rs3865444 at CD33, pBMI  = 0.024). (3) SNPs at two of the obesity risk loci (rs4836133 downstream of ZNF608; pAD  = 0.002 and at rs713586 downstream of RBJ/DNAJC27; pAD  = 0.018) were nominally associated with AD risk. Additionally, among the SNPs used for confirmation in both studies the AD risk allele of rs1858973, with an AD association just below genome-wide significance (pAD  = 7.20 × 10(-07)), was also associated with obesity (SNP at IQCK/GPRC5B; pBMI  = 5.21 × 10(-06) ; pcorr  = 3.24 × 10(-04)). Our first GWAS based cross-disorder analysis for AD and obesity suggests that rs10838725 at the locus CELF1 might be relevant for both disorders. Show less

In this study we have used mass spectrometry in order to characterize the HDL lipidome in three groups of women from the DIWA cohort; one control group, plus two groups with type 2 diabetes with insulin resistance; one dyslipidemic and one normolipidemic. The aim was to investigate whether dyslipidemia is required in addition to insulin resistance for the occurrence of an altered HDL lipidome, which in turn might impact HDL functionality. The dyslipidemic type 2 diabetic subjects were distinguished by obesity, hypertriglyceridemia with elevated apoC3, low HDL-cholesterol and chronic low grade inflammation. In a stepwise multivariate linear regression analysis, including biomarkers of dyslipidemia and insulin resistance as independent variables, only dyslipidemia showed a significant correlation with HDL lipid classes. Small HDL-particles predominated in dyslipidemic subjects in contrast to the normolipidemic diabetic and control groups, and were enriched in lysophosphatidylcholine (+13%), a product of proinflammatory phospholipases, and equally in two core lipids, palmitate-rich triacylglycerols and diacylglycerols (+77 %), thereby reflecting elevated CETP activity. Dyslipidemic small HDL particles were further distinguished not only as the primary carrier of ceramides, which promote inflammation and insulin resistance, but also by a subnormal plasmalogen/apoAI ratio, consistent with elevated oxidative stress typical of type 2 diabetes. From these data we conclude that in type 2 diabetes, dyslipidemia predominates relative to hyperglycemia for the occurrence of an altered HDL lipidome. Furthermore, dyslipidemia alters the cargo of bioactive lipids, with implications for HDL function. Show less

Spermiogenesis is a postmeiotic process that drives development of round spermatids into fully elongated spermatozoa. Spermatid elongation is largely controlled post-transcriptionally after global silencing of mRNA synthesis from the haploid genome. Here, rats that differentially express EGFP from a lentiviral transgene during early and late steps of spermiogenesis were used to flow sort fractions of round and elongating spermatids. Mass-spectral analysis of 2D gel protein spots enriched >3-fold in each fraction revealed a heterogeneous RNA binding proteome (hnRNPA2/b1, hnRNPA3, hnRPDL, hnRNPK, hnRNPL, hnRNPM, PABPC1, PABPC4, PCBP1, PCBP3, PTBP2, PSIP1, RGSL1, RUVBL2, SARNP2, TDRD6, TDRD7) abundantly expressed in round spermatids prior to their elongation. Notably, each protein within this ontology cluster regulates alternative splicing, sub-cellular transport, degradation and/or translational repression of mRNAs. In contrast, elongating spermatid fractions were enriched with glycolytic enzymes, redox enzymes and protein synthesis factors. Retrogene-encoded proteins were over-represented among the most abundant elongating spermatid factors identified. Consistent with these biochemical activities, plus corresponding histological profiles, the identified RNA processing factors are predicted to collectively drive post-transcriptional expression of an alternative exome that fuels finishing steps of sperm maturation and fitness. Show less

Mice have been used widely to define the mechanism of action of fibric acid derivatives. The fibrates are pharmacological agonists of the peroxisome proliferator-activated receptor alpha (PPARalpha), whose activation in human subjects promotes potent reduction in plasma levels of triglycerides (TG) with concomitant increase in those of HDL-cholesterol. The impact of PPARalpha agonists on gene expression in humans and rodents is however distinct; such distinctions include differential regulation of key genes of lipid metabolism. We evaluated the question as to whether the human and murine genes encoding apolipoprotein apoAV, a regulator of plasma concentrations of TG-rich lipoproteins, might be differentially regulated in response to fibrates. Fenofibrate, a classic PPARalpha agonist, repressed expression of mouse Apoa5 in vivo in a mouse model transgenic for the human APOA5 gene; by contrast, expression of the human ortholog was up-regulated. Our findings are consistent with the presence of a functional PPAR-binding element in the promoter of the human APOA5 gene; this element is however degenerate and non-functional in the corresponding mouse Apoa5 sequence, as demonstrated by reporter assays and gel shift analyses. These data further highlights the distinct mechanisms which are implicated in the metabolism of TG-rich lipoproteins in mice as compared to man. They equally emphasize the importance of the choice of a mouse model for investigation of the impact of pharmaceutical modifiers on hypertriglyceridemia. Show less

The apolipoprotein AV gene (APOA5) is a key determinant of plasma triglyceride levels, a major risk factor for coronary artery disease and a biomarker for the metabolic syndrome. Since thyroid hormones influence very low density lipoprotein triglyceride metabolism and clinical studies have demonstrated an inverse correlation between thyroid status and plasma triglyceride levels, we examined whether APOA5 is regulated by thyroid hormone. Here we report that 3,5,3'-triiodo-L-thyronine (T3) and a synthetic thyroid receptor beta (TRbeta) ligand increase APOA5 mRNA and protein levels in hepatocytes. Our data revealed that T3-activated TR directly regulates APOA5 promoter through a functional direct repeat separated by four nucleotides (DR4). Interestingly, we show that upstream stimulatory factor 1, a transcription factor associated with familial combined hyperlipidemia and elevated triglyceride levels in humans, and upstream stimulatory factor 2 cooperate with TR, resulting in a synergistic activation of APOA5 promoter in a ligand-dependent manner via an adjacent E-box motif. In rats, we observed that apoAV levels declines with thyroid hormone depletion but returned to normal levels upon T3 administration. In addition, treatments with a TRbeta-selective agonist increased apoAV and diminished triglyceride levels. The identification of APOA5 as a T3 target gene provides a new potential mechanism whereby thyroid hormones can influence triglyceride homeostasis. Additionally, these data suggest that TRbeta may be a potential pharmacological target for the treatment of hypertriglyceridemia. Show less

Hereditary multiple exostoses (EXT) is an autosomal dominant disorder characterized by growth of benign bone tumors. Three chromosomal loci have been implicated in this genetically heterogeneous disease: EXT1 at 8q24, EXT2 at 11p13, and EXT3 on 19p. EXT1 and EXT2 were recently cloned. We evaluated 34 families with EXT to estimate the proportion of disease attributable to EXT1, EXT2, and EXT3 and to investigate the spectrum of EXT1 mutations. Linkage analyses combined with heterogeneity testing provides strong evidence in favor of linkage of disease to both chromosomes 8 and 11, but does not support evidence of linkage to chromosome 19 in this data set. The 11 EXT1 exons were PCR-amplified and sequenced in all 11 isolated cases and in 20 of the 23 familial cases. Twelve different novel EXT1 mutations were detected, including 5 frame-shift deletions or insertions, 1 codon deletion, and 6 single base-pair substitutions distributed across 8 of the exons. Only 2 of the mutations were detected in more than one family. Three mutations affect sites in which alterations were previously reported. Nonchain-terminating missense mutations were identified in codons 280 and 340, both coding for conserved arginine residues. These residues may be crucial to the function of this protein. Although the prevalence of EXT has been estimated to be approximately 1/50,000 individuals, the disease has been reported to occur much more frequently in the Chamorro natives on Guam. Our detection of an EXT1 mutation in one Chamorro subject will allow investigation of a possible founder effect in this population. Combined mutational and heterogeneity analyses in this set of families with multiple exostoses suggest that 66% of our total sample, including 45% of isolated and 77% of familial cases, are attributable to abnormalities in EXT1. Show less

We have recently cloned a cDNA encoding the human phenol-preferring phenol sulfotransferase (P-PST) enzyme. An oligonucleotide primer pair based on the human STP (representing sulfotransferase, phenol-preferring) cDNA sequence was synthesized and was employed in polymerase chain reaction (PCR) amplification of human genomic DNA to identify a 525-bp DNA fragment. The DNA sequence of this portion of the STP gene, near the 5' end of the coding region, was determined. The amplified genomic fragment contained two small introns of 104 and 89 bp. When DNA samples from a human-hamster somatic cell hybrid panel were screened by PCR using these primers, only those hybrids that contained human chromosome 16 were positive for the 525-bp genomic fragment. To identify the specific region on chromosome 16 that contained the STP gene, PCR amplification reactions were performed on a human-mouse somatic cell hybrid panel containing defined portions of human chromosome 16. The results indicated that STP is localized proximal to the gene for protein kinase C, beta 1 polypeptide (PRKCB1), in the region from the distal portion of 16p11.2 to p12.1. The human STP gene maps near the locus for Batten disease (CLN3). Furthermore, we have determined by genotyping of murine interspecific backcross progeny that the homologous gene in mouse (Stp) localizes to the syntenic region of mouse chromosome 7 near the D7Mit8 (at 54 cM) and D7Bir1 markers. Show less