👤 Annett Kohl

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

Statins induce plaque regression characterized by reduced macrophage content in humans, but the underlying mechanisms remain speculative. Studying the translational APOE*3-Leiden.CETP mouse model with a humanized lipoprotein metabolism, we find that systemic cholesterol lowering by oral atorvastatin or dietary restriction inhibits monocyte infiltration, and reverses macrophage accumulation in atherosclerotic plaques. Contrary to current believes, none of (1) reduced monocyte influx (studied by cell fate mapping in thorax-shielded irradiation bone marrow chimeras), (2) enhanced macrophage egress (studied by fluorescent bead labeling and transfer), or (3) atorvastatin accumulation in murine or human plaque (assessed by mass spectrometry) could adequately account for the observed loss in macrophage content in plaques that undergo phenotypic regression. Instead, suppression of local proliferation of macrophages dominates phenotypic plaque regression in response to cholesterol lowering: the lower the levels of serum LDL-cholesterol and lipid contents in murine aortic and human carotid artery plaques, the lower the rates of in situ macrophage proliferation. Our study identifies macrophage proliferation as the predominant turnover determinant and an attractive target for inducing plaque regression. Show less

While nuclear lamina abnormalities are hallmarks of human diseases, their interplay with epigenetic regulators and precise epigenetic landscape remain poorly understood. Here, we show that loss of the lysine acetyltransferase MOF or its associated NSL-complex members KANSL2 or KANSL3 leads to a stochastic accumulation of nuclear abnormalities with genomic instability patterns including chromothripsis. SILAC-based MOF and KANSL2 acetylomes identified lamin A/C as an acetylation target of MOF. HDAC inhibition or acetylation-mimicking lamin A derivatives rescue nuclear abnormalities observed in MOF-deficient cells. Mechanistically, loss of lamin A/C acetylation resulted in its increased solubility, defective phosphorylation dynamics and impaired nuclear mechanostability. We found that nuclear abnormalities include EZH2-dependent histone H3 Lys 27 trimethylation and loss of nascent transcription. We term this altered epigenetic landscape "heterochromatin enrichment in nuclear abnormalities" (HENA). Collectively, the NSL-complex-dependent lamin A/C acetylation provides a mechanism that maintains nuclear architecture and genome integrity. Show less

One of the most common side effects of orthodontic treatment is root resorption on the pressure side of tooth movement. This is usually repaired by cementoblasts, but 1-5 % of patients eventually experiences a marked reduction in root length because no repair has occurred. The reason why cementoblasts should lose their repair function in such cases is not well understood. There is evidence from genome-wide expression analysis (Illumina HumanHT-12 v4 Expression BeadChip Kit; > 30,000 genes) that apoptotic processes are upregulated after the compression of cementoblasts, which is particularly true of the pro-apoptotic gene AXUD1. Human primary cementoblasts (HPCBs) from two individuals were subjected to compressive loading at 30 g/cm(2) for 1/6/10 h. The cells were then evaluated for apoptosis by flow cytometry, for mRNA expression of putative genes (AXUD1, AXIN1, AXIN2) by quantitative PCR, and for involvement of c-Jun-N-terminal kinases (JNKs) in the regulation of AXUD1 via western blotting. In addition, platelet-derived growth factor receptor-β (PDGFRβ) was selectively inhibited by SU16f to analyze the effect of PDGFRβ-dependent signal transduction on AXUD1 and AXIN1 expression. The percentage of apoptotic HPCBs rose after only 6 h of compressive loading, and 18-20 % of cells were apoptotic after 10 h. Microarray data revealed significant upregulation of the pro-apoptotic gene AXUD1 after 6 h and quantitative PCR significant AXUD1 upregulation after 6 and 10 h of compression. AXIN1 and AXIN2 expression in HPCBs was significantly increased after compressive loading. Our tests also revealed that PDGFRβ signaling inhibition by SU16f augmented the expression of AXIN1 and AXUD1 in HPCBs under compression. Increased apoptosis of compressed HPCBs might help explain why cementoblasts, rather than invariably repairing all cases of root resorption, sometimes allow the original root length to shorten. The pathway hypothesized to lead to cementoblast apoptosis involves PDGF signaling, with this signal transduction's inhibition augmenting the expression of pro-apoptotic genes. Thus activating PDGF signaling may modify the signaling pathway for the apoptosis of cementoblasts, which would reveal a protective role of PDGF for these cells. Further studies are needed to develop strategies of treatment capable of minimizing root resorption. Show less