Tapia-Paez, I. | Search bioRxiv

bioRxiv2023

Rare coding variants in NOX4 link high superoxide levels to psoriatic arthritis mutilans

Psoriatic arthritis mutilans (PAM) is the rarest and most severe form of psoriatic arthritis. PAM is characterized by erosions of the small joints of hands and feet and osteolysis leading to joint disruption. Despite its severity, the underlying mechanisms are unknown, and no candidate susceptibility genes have hitherto been identified. We aimed to investigate the genetic basis of PAM. We performed massive parallel sequencing of sixty-one patients genomes from the PAM Nordic cohort. We validated the rare variants found by Sanger sequencing and genotyped additional psoriasis, psoriatic arthritis, and control cohorts. We then tested the role of the variants using in vivo and in vitro models. We found rare variants with a minor allele frequency (MAF) below 0.0001 in the NADPH oxidase 4 (NOX4) in four patients. In silico predictions show that the identified variants are potentially damaging. NOXs are the only enzymes producing reactive oxygen species (ROS). ROS are highly reactive molecules important role in the regulation of signal transduction. NOX4 is specifically involved in the differentiation of osteoclasts, the cells implicated in bone resorption. Functional follow-up studies using cell culture, zebrafish models, and measurement of ROS in patients uncovered that the NOX4 variants found in this study increase the levels of ROS both in vitro and in vivo. We propose NOX4 as the first candidate susceptibility gene for PAM. Our study links high levels of ROS caused by NOX4 variants to the development of PAM, opening the possibility for a potential therapeutic target.

genetics↗

bioRxiv2020

Rare variants in dynein heavy chain genes in two individuals with situs inversus and developmental dyslexia

BackgroundDevelopmental dyslexia (DD) is a neurodevelopmental learning disorder with high heritability. A number of candidate susceptibility genes have been identified, some of which are linked to the function of the cilium, an organelle regulating left-right asymmetry development in the embryo. Furthermore, it has been suggested that disrupted left-right asymmetry of the brain may play a role in neurodevelopmental disorders such as DD. MethodsHere, we studied two individuals with co-occurring situs inversus (SI) and DD using whole genome sequencing to identify single nucleotide variants or copy number variations of importance for DD and SI. ResultsIndividual 1 had primary ciliary dyskinesia (PCD), a rare, autosomal recessive disorder with oto-sino-pulmonary phenotype and SI. We identified two rare nonsynonymous variants in the dynein axonemal heavy chain 5 gene (DNAH5): c.7502G>C;p.(R2501P), a previously reported variant predicted to be damaging and c.12043T>G;p.(Y4015D), a novel variant predicted to be damaging. Ultrastructural analysis of the cilia revealed a lack of outer dynein arms and normal inner dynein arms. MRI of the brain revealed no significant abnormalities. Individual 2 had non-syndromic SI and DD. In individual 2, one rare variant (c.9110A>G;p.(H3037R)) in the dynein axonemal heavy chain 11 gene (DNAH11), coding for another component of the outer dynein arm, was identified. ConclusionsWe identified the likely genetic cause of SI and PCD in one individual, and a possibly significant heterozygosity in the other, both involving dynein genes. Given the present evidence, it is unclear if the identified variants also predispose to DD, but further studies into the association are warranted.

genetics↗