Bi-allelic mutation in SEC16B alters collagen trafficking and increases ER stress
Ontology highlight
ABSTRACT:
SUBMITTER: Dr. Ahmed El-Gazzar
PROVIDER: S-SCDT-10_15252-EMMM_202216834 | biostudies-other |
REPOSITORIES: biostudies-other
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Project description:Osteogenesis imperfecta (OI) is a genetically and clinically heterogeneous disorder characterized by bone fragility and reduced bone mass generally caused by defects in type I collagen structure or defects in proteins interacting with collagen processing. We identified a homozygous missense mutation in SEC16B in a child with vertebral fractures, leg bowing, short stature, muscular hypotonia, and bone densitometric and histomorphometric features in keeping with OI with distinct ultrastructural features. In line with the putative function of SEC16B as a regulator of trafficking between the ER and the Golgi complex, we showed that patient fibroblasts accumulated type I procollagen in the ER and exhibited a general trafficking defect at the level of the ER. Consequently, patient fibroblasts exhibited ER stress, enhanced autophagosome formation, and higher levels of apoptosis. Transfection of wild-type SEC16B into patient cells rescued the collagen trafficking. Mechanistically, we show that the defect is a consequence of reduced SEC16B expression, rather than due to alterations in protein function. These data suggest SEC16B as a recessive candidate gene for OI.
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Project description:BackgroundAutosomal recessive non-syndromic hearing loss (ARNSHL) is genetically and phenotypically heterogeneous with over 110 genes causally implicated in syndromic and non-syndromic hearing loss. Here, we investigate the genetic etiology of deafness in two GJB2 and GJB6 negative patients presenting with pre-lingual, progressive, severe hearing loss.MethodsTargeted exome sequencing (TES) using Next Generation Illumina Sequencing was used to analyze the exonic and some other important genomic regions of 154 genes in the proband. Subsequently, the mutation found was confirmed by Sanger sequencing in other affected sibling and healthy family members. The possible impact of the reported mutation on the corresponding protein was also evaluated by using bioinformatics tools. Moreover, the affected patients underwent audiological and ophthalmic evaluations.ResultsTES identified a novel homozygous missense mutation c.251T>C (p.I84T) in exon 3 of PDZD7 gene. In addition, segregation and phenotype-genotype correlation analysis as well as in-silico evaluations confirmed the autosomal recessive inheritance pattern and disease-causing nature of mutation found.ConclusionsIn overall, our finding could expand the pathogenic mutations spectrum and strengthens the clinical importance of the PDZD7 gene in ARNSHL patients. It can also aid to conduct genetic counseling, prenatal diagnosis and clinical management of these types of genetic disorders.
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Project description:Mutations in the IDH1 and IDH2 genes encoding isocitrate dehydrogenases are frequent in human glioblastomas1 and cytogenetically normal acute myeloid leukemias (AML)2. These alterations are gain-of-function mutations in that they drive the synthesis of the “oncometabolite” R-2-hydroxyglutarate (2HG)3. It remains unclear how IDH1 and IDH2 mutations modify myeloid cell development and promote leukemogenesis. Here we report the characterization of conditional knock-in mice in which the most common IDH1 mutation, Idh1-R132H, is inserted into the endogenous murine Idh1 locus and is expressed in cells of the hematopoietic (Vav-KI) or more specifically in cells of the myeloid (LysM-KI) lineage. These mutants show increased numbers of early hematopoietic progenitors and develop splenomegaly and anemia with extramedullary hematopoiesis, suggesting a dysfunctional bone marrow niche. Furthermore, LysM-KI cells exhibit both hypermethylated histones and changes to DNA methylation similar to those observed in human IDH1/2-mutant AML. Thus, our study is the first to describe the generation of conditional Idh1-R132H-KI mice. Furthermore, our study is also the first report showing the induction of a leukemic DNA methylation signature in a modeled system and sheds light on the mechanistic links between IDH1 mutation and human AML.
2012-07-22 | GSE38687 | GEO