Biomedical subjects

Oguz Kanca

Publications and source records attributed to Oguz Kanca.

3 recordsLinked to original sources

PubMed2026

Uncovering phenotypic expansion in AXIN2-related disorders through precision animal modeling.

PURPOSE: Heterozygous pathogenic variants in AXIN2 (HGNC: 904) cause oligodontia-colorectal cancer syndrome. We identified 5 individuals with de novo heterozygous variants [NM_004655.4:c.196G>A p.(Glu66Lys), c.197A>G p.(Glu66Gly), and c.199G>A p.(Gly67Arg)] in AXIN2. Common phenotypes among these individuals included ectodermal dysplasia, global developmental delay, microcephaly, and limb, ophthalmologic, and genitourinary abnormalities. METHODS: Structural modeling was performed to predict the impact of these variants on AXIN2. A prime editing N1 screen of mouse embryos was performed to test whether the p.Glu66Lys variant produces a phenotype. Drosophila models were used to test the effect of this variant on Wnt signaling. RESULTS: Structural modeling suggests that these variants disrupt AXIN2 binding to tankyrase, which regulates AXIN2 levels through poly-ADP-ribosylation. Heterozygous (p.Glu66Lys) mouse embryos were perinatally lethal with soft palate clefts and skeletal abnormalities. Modeling of the p.Glu66Lys variant in the Drosophila wing suggests gain-of-function or dominant-negative activity compared to reference AXIN2. CONCLUSION: Specific variants in the tankyrase-binding domain of AXIN2 are pathogenic, leading to phenotypic expansion with potential context-dependent effects on AXIN2 function and Wnt signaling. The N1 modeling strategy used to demonstrate variant pathogenicity may be beneficial for resolving other heterozygous variants associated with congenital anomalies.

AXIN2↗

PubMed2024

Loss-of-function in RBBP5 results in a syndromic neurodevelopmental disorder associated with microcephaly.

PURPOSE: Epigenetic dysregulation has been associated with many inherited disorders. RBBP5 (HGNC:9888) encodes a core member of the protein complex that methylates histone 3 lysine-4 and has not been implicated in human disease. METHODS: We identify 5 unrelated individuals with de novo heterozygous variants in RBBP5. Three nonsense/frameshift and 2 missense variants were identified in probands with neurodevelopmental symptoms, including global developmental delay, intellectual disability, microcephaly, and short stature. Here, we investigate the pathogenicity of the variants through protein structural analysis and transgenic Drosophila models. RESULTS: Both missense p.(T232I) and p.(E296D) variants affect evolutionarily conserved amino acids located at the interface between RBBP5 and the nucleosome. In Drosophila, overexpression analysis identifies partial loss-of-function mechanisms when the variants are expressed using the fly Rbbp5 or human RBBP5 cDNA. Loss of Rbbp5 leads to a reduction in brain size. The human reference or variant transgenes fail to rescue this loss and expression of either missense variant in an Rbbp5 null background results in a less severe microcephaly phenotype than the human reference, indicating both missense variants are partial loss-of-function alleles. CONCLUSION: Haploinsufficiency of RBBP5 observed through de novo null and hypomorphic loss-of-function variants is associated with a syndromic neurodevelopmental disorder.

Humans↗

PubMed2023

De novo variants in MRTFB have gain-of-function activity in Drosophila and are associated with a novel neurodevelopmental phenotype with dysmorphic features.

PURPOSE: Myocardin-related transcription factor B (MRTFB) is an important transcriptional regulator, which promotes the activity of an estimated 300 genes but is not known to underlie a Mendelian disorder. METHODS: Probands were identified through the efforts of the Undiagnosed Disease Network. Because the MRTFB protein is highly conserved between vertebrate and invertebrate model organisms, we generated a humanized Drosophila model expressing the human MRTFB protein in the same spatial and temporal pattern as the fly gene. Actin binding assays were used to validate the effect of the variants on MRTFB. RESULTS: Here, we report 2 pediatric probands with de novo variants in MRTFB (p.R104G and p.A91P) and mild dysmorphic features, intellectual disability, global developmental delays, speech apraxia, and impulse control issues. Expression of the variants within wing tissues of a fruit fly model resulted in changes in wing morphology. The MRTFBR104G and MRTFBA91P variants also display a decreased level of actin binding within critical RPEL domains, resulting in increased transcriptional activity and changes in the organization of the actin cytoskeleton. CONCLUSION: The MRTFBR104G and MRTFBA91P variants affect the regulation of the protein and underlie a novel neurodevelopmental disorder. Overall, our data suggest that these variants act as a gain of function.

Animals↗