👤 Tobias Haack

Megacystis-Microcolon-Intestinal Hypoperistalsis Syndrome (MMIHS) is a rare genetic visceral myopathy, with a historically high mortality rate. Its genetic and phenotypic variability and management options remain poorly characterized. This study correlates genotype with phenotype and subsequently analyzes treatment and outcome of patients with pediatric-onset MMIHS. We retrospectively analyzed 26 MMIHS patients (median age 97 months, 62% female) with molecular diagnostics in 19 patients at a German quaternary intestinal rehabilitation center followed between 2012 and 2025. In this second-largest pediatric MMIHS cohort worldwide, genotype correlated with severity and outcomes, with Show less

A homozygous loss-of-function (LoF) variant in POC5 was previously described in an individual with retinitis pigmentosa. We identified POC5 variants in 12 probands with a syndromic phenotype. We aim to define the phenotype spectrum and molecular mechanism associated with biallelic POC5 LoF variants. We studied a cohort of 12 families with bi-allelic LoF POC5 variants and performed detailed phenotype analysis. POC5 localization studies were performed in 3 proband-derived fibroblast cell lines. Detailed phenotyping of probands with POC5 variants expands the phenotype spectrum beyond ocular manifestations. This syndrome causes not only rod-cone dystrophy but also diabetes mellitus with severe insulin resistance and partial lipodystrophy, kidney disease, and muscle cramps. The POC5 protein plays an essential role during cell cycle and cilium formation. Interestingly, POC5 localization studies in 3 proband-derived fibroblast cell lines show aberrant localization suggesting a ciliary defect. The phenotypes of the 12 families in this study fit well within the ciliopathy phenotype spectrum, except for lipodystrophy, which is not common in ciliopathies. We describe a multiorgan syndrome caused by bi-allelic LoF variants in POC5. This underscores the pleiotropic effects of POC5 variants and highlights the significance of adipose tissue and metabolic dysfunction in ciliopathies. Show less

Imaging and radiotherapy targeting the glucose-dependent insulinotropic polypeptide receptor (GIPR) could potentially benefit the management of neuroendocrine neoplasms (NENs), complementing clinically established radiopharmaceuticals. The aim of this study was to evaluate a GIPR-targeting positron emission tomography (PET) radioligand with receptor-specific binding, fast blood clearance, and low liver background uptake. The peptide DOTA-bioconjugate, C803-GIP, was developed based on the sequence of the endogenous GIP(1-30) and synthetic exendin-4 peptides with selective amino acid mutations to combine their specificity for the GIPR and in vivo stability, respectively. The Show less

Targeting of the glucose-dependent insulinotropic polypeptide receptor (GIPR) is an emerging strategy in antidiabetic drug development. The aim of this study was to develop a positron emission tomography (PET) radioligand for the GIPR to enable the assessment of target distribution and drug target engagement in vivo. The GIPR-selective peptide S02-GIP was radiolabeled with Show less

To test specific mono-agonists to the glucagon-like peptide-1 receptor (GLP-1R), glucagon receptor (GCGR) and glucose-dependent insulinotropic peptide receptor (GIPR), individually and in combination, in a mouse model of diet-induced non-alcoholic steatohepatitis (NASH) and fibrosis in order to decipher the contribution of their activities and potential additive effects to improving systemic and hepatic metabolism. We induced NASH by pre-feeding C57BL/6J mice a diet rich in fat, fructose and cholesterol for 36 weeks. This was followed by 8 weeks of treatment with the receptor-specific agonists 1-GCG (20 μg/kg twice daily), 2-GLP1 (3 μg/kg twice daily) or 3-GIP (30 μg/kg twice daily), or the dual (1 + 2) or triple (1 + 2 + 3) combinations thereof. A dual GLP-1R/GCGR agonistic peptide, 4-dual-GLP1/GCGR (30 μg/kg twice daily), and liraglutide (100 μg/kg twice daily) were included as references. Whereas low-dose 1-GCG or 3-GIP alone did not influence body weight, liver lipids and histology, their combination with 2-GLP1 provided additional weight loss, reduction in liver triglycerides and improvement in histological disease activity score. Notably, 4-dual-GLP-1R/GCGR and the triple combination of selective mono-agonists led to a significantly stronger reduction in the histological non-alcoholic fatty liver disease activity score compared to high-dose liraglutide, at the same extent of body weight loss. GCGR and GIPR agonism provide additional, body weight-independent improvements on top of GLP-1R agonism in a murine model of manifest NASH with fibrosis. Show less

Non-neuronal optogenetic approaches empower precise regulation of protein dynamics in live cells but often require target-specific protein engineering. To address this challenge, we developed a generalizable light-modulated protein stabilization system (GLIMPSe) to control the intracellular protein level independent of its functionality. We applied GLIMPSe to control two distinct classes of proteins: mitogen-activated protein kinase phosphatase 3 (MKP3), a negative regulator of the extracellular signal-regulated kinase (ERK) pathway, and a constitutively active form of MEK (CA MEK), a positive regulator of the same pathway. Kinetics study showed that light-induced protein stabilization could be achieved within 30 min of blue light stimulation. GLIMPSe enables target-independent optogenetic control of protein activities and therefore minimizes the systematic variation embedded within different photoactivatable proteins. Overall, GLIMPSe promises to achieve light-mediated post-translational stabilization of a wide array of target proteins in live cells. Show less

The urea cycle disorder carbamoyl phosphate synthetase I deficiency is an important differential diagnosis in the encephalopathic neonate. This intoxication type inborn error of metabolism often leads to neonatal death or severe and irreversible damage of the central nervous system, even despite appropriate treatment. Timely diagnosis is crucial, but can be difficult on routine metabolite level. Here, we report ten neonates from eight families (finally) diagnosed with CPS1 deficiency at three tertiary metabolic centres. In seven of them the laboratory findings were dominated by significantly elevated urinary 3-methylglutaconic acid levels which complicated the diagnostic process. Our findings are both important for the differential diagnosis of patients with urea cycle disorders and also broaden the differential diagnosis of hyperammonemia associated with 3-methylglutaconic aciduria, which was earlier only reported in TMEM70 and SERAC1 defect. Show less

CLN3 disease (Spielmeyer-Vogt-Sjogren-Batten disease) is a severe pediatric neurodegenerative disorder for which there is currently no effective treatment. The disease is characterized by progressive neuronal death, which may be triggered by abnormal intracellular calcium levels leading to neuronal apoptosis. Previously, we demonstrated reversal of the calcium effect in a neuroblastoma cell line using amlodipine and other calcium channel antagonists. In the present studies, we developed a CLN3 siRNA-inhibited primary rat neuron model to further study etoposide-induced calcium changes and apoptosis in CLN3 disease followed by recovery experiments with amlodipine. Our results show that intracellular calcium is significantly elevated in siRNA-inhibited cortical neurons after potassium chloride-induced depolarization. We were also able to show that amlodipine, a predominantly L-type dihydropyrimidine calcium channel antagonist can reverse the aberrant calcium elevations in this model of the disease. We performed an in situ TUNEL assay following etoposide-exposure to siRNA inhibited primary neurons, and apoptotic nuclei were detected providing additional evidence that increased neuronal apoptosis is associated with increased calcium levels. Amlodipine also reduced the absolute number of apoptotic cells in this experimental model. Show less

Genetic variants responsible for susceptibility to obesity and its comorbidities among Hispanic children have not been identified. The VIVA LA FAMILIA Study was designed to genetically map childhood obesity and associated biological processes in the Hispanic population. A genome-wide association study (GWAS) entailed genotyping 1.1 million single nucleotide polymorphisms (SNPs) using the Illumina Infinium technology in 815 children. Measured genotype analysis was performed between genetic markers and obesity-related traits i.e., anthropometry, body composition, growth, metabolites, hormones, inflammation, diet, energy expenditure, substrate utilization and physical activity. Identified genome-wide significant loci: 1) corroborated genes implicated in other studies (MTNR1B, ZNF259/APOA5, XPA/FOXE1 (TTF-2), DARC, CCR3, ABO); 2) localized novel genes in plausible biological pathways (PCSK2, ARHGAP11A, CHRNA3); and 3) revealed novel genes with unknown function in obesity pathogenesis (MATK, COL4A1). Salient findings include a nonsynonymous SNP (rs1056513) in INADL (p = 1.2E-07) for weight; an intronic variant in MTNR1B associated with fasting glucose (p = 3.7E-08); variants in the APOA5-ZNF259 region associated with triglycerides (p = 2.5-4.8E-08); an intronic variant in PCSK2 associated with total antioxidants (p = 7.6E-08); a block of 23 SNPs in XPA/FOXE1 (TTF-2) associated with serum TSH (p = 5.5E-08 to 1.0E-09); a nonsynonymous SNP (p = 1.3E-21), an intronic SNP (p = 3.6E-13) in DARC identified for MCP-1; an intronic variant in ARHGAP11A associated with sleep duration (p = 5.0E-08); and, after adjusting for body weight, variants in MATK for total energy expenditure (p = 2.7E-08) and in CHRNA3 for sleeping energy expenditure (p = 6.0E-08). Unprecedented phenotyping and high-density SNP genotyping enabled localization of novel genetic loci associated with the pathophysiology of childhood obesity. Show less

The delta-5 and delta-6 desaturases (D5D and D6D), encoded by fatty acid desaturase 1 (FADS1) and 2 (FADS2) genes, respectively, are rate-limiting enzymes in the metabolism of ω-3 and ω-6 fatty acids. The objective of this study was to identify genes influencing variation in estimated D5D and D6D activities in plasma and erythrocytes in Alaskan Eskimos (n = 761) participating in the genetics of coronary artery disease in Alaska Natives (GOCADAN) study. Desaturase activity was estimated by product: precursor ratio of polyunsaturated fatty acids. We found evidence of linkage for estimated erythrocyte D5D (eD5D) on chromosome 11q12-q13 (logarithm of odds score = 3.5). The confidence interval contains candidate genes FADS1, FADS2, 7-dehydrocholesterol reductase (DHCR7), and carnitine palmitoyl transferase 1A, liver (CPT1A). Measured genotype analysis found association between CPT1A, FADS1, and FADS2 single-nucleotide polymorphisms (SNPs) and estimated eD5D activity (p-values between 10(-28) and 10(-5)). A Bayesian quantitative trait nucleotide analysis showed that rs3019594 in CPT1A, rs174541 in FADS1, and rs174568 in FADS2 had posterior probabilities > 0.8, thereby demonstrating significant statistical support for a functional effect on eD5D activity. Highly significant associations of FADS1, FADS2, and CPT1A transcripts with their respective SNPs (p-values between 10(-75) and 10(-7)) in Mexican Americans of the San Antonio Family Heart Study corroborated our results. These findings strongly suggest a functional role for FADS1, FADS2, and CPT1A SNPs in the variation in eD5D activity. Show less

Defects of the CLN3 gene on chromosome 16p12.1 lead to the juvenile form of neuronal ceroid-lipofuscinosis (JNCL, Batten Disease), the most common recessive inherited neurodegenerative disorder in children. Dysregulation of intracellular calcium homeostasis in the absence of a functional CLN3 protein (CLN3P, Battenin) has been linked to synaptic dysfunction and accelerated apoptosis in vulnerable neuronal cells. Prolonged increase of intracellular calcium concentration is considered to be a significant trigger for neuronal apoptosis and cellular loss in JNCL. We examined the potential effect of 41 different calcium channel modulators on intracellular calcium concentration in CLN3 siRNA knock down SH-SY5Y neuroblastoma cells. Six drugs belonging to the group of voltage dependent L-type channel blockers show significant lowering of the increased intracellular calcium levels in CLN3 siRNA knock down cells. Our studies provide important new data suggesting possible beneficial effects of the tested drugs on calcium flux regulated pathways in neuronal cell death. Therapeutic intervention in this untreatable disease will likely require drugs that cross the blood-brain barrier as did all of the positively screened drugs in this study. Better comprehension of the mechanism of neurodegeneration in rare recessive disorders, such as neuronal ceroid-lipofuscinoses, is likely to help to better understand mechanisms involved in more complex genetic neurodegenerative conditions, such as those associated with aging. Show less