Biology subjects

Bonkowsky, J. L.

Publications and source records attributed to Bonkowsky, J. L..

3 recordsLinked to original sources

bioRxiv2025

ATAD1 Overexpression Enhances Mitochondrial and Peroxisomal Function in Zellweger Syndrome Disorder Models

Zellweger Spectrum Disorders (ZSDs) are caused by mutations in any of the different peroxin (PEX) genes, which are essential for peroxisome biogenesis and function. Clinical features of ZSDs include seizures, leukodystrophy, renal and liver dysfunction, skeletal abnormalities, and they usually result in death during infancy or early childhood. There are no treatments for ZSDs, and their rarity, the large size of the PEX genes, and the numerous different genes, has impaired therapeutic development. We previously demonstrated that ATAD1, a mitochondrial protein quality control chaperone, could correct both mitochondrial and peroxisomal phenotypes in PEX3 patient fibroblasts. In this study, we investigated whether overexpressing ATAD1 could provide similar benefits in PEX1 and PEX6 patient cell lines, which account for over 70% of ZSD cases. We used established PEX6-/- HEK293 cells, patient-derived fibroblasts with pathogenic PEX1 mutations, and newly created zebrafish mutants. Lipidomic profiling of the cell lines demonstrated widespread dysregulation, including accumulation of lysophosphatidylcholines with very-long-chain fatty acids, depletion of plasmalogens and cholesteryl esters containing polyunsaturated fatty acids, and a decrease in cardiolipins. Overexpressing ATAD1 partly corrected these imbalances, including normalizing VLCFA metabolism in PEX1 fibroblasts and restoring plasmalogens and cardiolipins in PEX6-deficient cells. Mitochondrial function analysis (Seahorse XF) showed that ATAD1 increased basal and ATP-linked respiration in both PEX1- and PEX6-deficient cells, sometimes surpassing the effects of PEX gene re-expression. ATAD1 increased peroxisome numbers in both PEX6 and PEX1 cells. Zebrafish Pex1 mutants exhibited impaired maximal respiration despite normal basal activity, confirming mitochondrial vulnerability in vivo. These findings further confirm a role for ATAD1 as a modifier that improves lipid metabolism, mitochondrial function, and peroxisome abundance that could function across multiple ZSDs.

neuroscience↗

bioRxiv2024

Identification of CNTN2 as a genetic modifier of PIGA-CDG through pedigree analysis of a family with incomplete penetrance and functional testing in Drosophila

Loss of function mutations in the X-linked PIGA gene lead to PIGA-CDG, an ultra-rare congenital disorder of glycosylation (CDG), typically presenting with seizures, hypotonia, and neurodevelopmental delay. We identified two brothers (probands) with PIGA-CDG, presenting with epilepsy and mild developmental delay. Both probands carry PIGAS132C, an ultra-rare variant predicted to be damaging. Strikingly, the maternal grandfather and a great-uncle also carry PIGAS132C, but neither presents with symptoms associated with PIGA-CDG. We hypothesized genetic modifiers may contribute to this reduced penetrance. Using whole genome sequencing and pedigree analysis, we identified possible susceptibility variants found in the probands and not in carriers and possible protective variants found in the carriers and not in the probands. Candidate variants included heterozygous, damaging variants in three genes also involved directly in GPI-anchor biosynthesis and a few genes involved in other glycosylation pathways or encoding GPI-anchored proteins. We functionally tested the predicted modifiers using a Drosophila eye-based model of PIGA-CDG. We found that loss of CNTN2, a predicted protective modifier, rescues loss of PIGA in Drosophila eye-based model, like what we predict in the family. Further testing found that loss of CNTN2 also rescues patient-relevant phenotypes, including seizures and climbing defects in Drosophila neurological models of PIGA-CDG. By using pedigree information, genome sequencing, and in vivo testing, we identified CNTN2 as a strong candidate modifier that could explain the incomplete penetrance in this family. Identifying and studying rare disease modifier genes in human pedigrees may lead to pathways and targets that may be developed into therapies.

genetics↗

bioRxiv2018

Loss of TP73 function contributes to amyotrophic lateral sclerosis pathogenesis

Much remains unknown about the genetics and pathophysiology underlying the neurodegenerative disease amyotrophic lateral sclerosis (ALS). We analyzed exome sequences from a cohort of 87 sporadic ALS (SALS) patients and 324 healthy individuals. TP73, a homolog of the TP53 tumor suppressor gene, had five rare deleterious protein-coding variants; in a separate collection of >2,900 ALS patients we identified an additional 19 rare deleterious variants in TP73. An in vitro C2C12 myoblast growth assay confirmed that these variants impair or alter TP73 function. In vivo mutagenesis of zebrafish tp73 using CRISPR led to impaired motor neuron development and abnormal axonal morphology, concordant with ALS pathology. Together, these results demonstrate that TP73 is a risk factor for ALS, and identifies a novel dysfunctional cellular process in the pathogenesis of ALS.

genetics↗