measuring-enzymatic-activity-neurodevelopmental-disorder-associated

Measuring Enzymatic Activity of Neurodevelopmental Disorder-Associated Deubiquitylating Enzymes via an In Vitro Ubiquitin Chain Cleavage Assay

Neurodevelopmental disorders (NDDs) are associated with impairments in nervous system function but often remain poorly understood at the molecular level. ...

Sanford Research

University of South Dakota

Intellectual disability (ID) represents a major burden on healthcare systems in the developed world. However, there is a disconnect between our knowledge of genes that are mutated in ID and our understanding of the underpinning molecular mechanisms that cause these disorders. We argue that elucidating the signalling and transcriptional networks that are dysregulated in patients will afford new therapeutic opportunities.

Therapeutic validation and targeting of signalling networks that are dysregulated in intellectual disability.

Neurodevelopmental disorders with intellectual disability (ND/ID) are a heterogeneous group of diseases driving lifelong deficits in cognition and behavior with no definitive cure. X-linked intellectual disability disorder 105 (XLID105, #300984; OMIM) is a ND/ID driven by hemizygous variants in the  gene encoding a protein deubiquitylase with a role in cell proliferation and neural development. Currently, only four genetically diagnosed individuals from two unrelated families have been described with limited clinical data. Furthermore, the mechanisms underlying the disorder are unknown. Here, we report 10 new XLID105 individuals from nine families and determine the impact of gene variants on USP27X protein function. Using a combination of clinical genetics, bioinformatics, biochemical, and cell biology approaches, we determined that XLID105 variants alter USP27X protein biology via distinct mechanisms including changes in developmentally relevant protein-protein interactions and deubiquitylating activity. Our data better define the phenotypic spectrum of XLID105 and suggest that XLID105 is driven by USP27X functional disruption. Understanding the pathogenic mechanisms of XLID105 variants will provide molecular insight into USP27X biology and may create the potential for therapy development.

 variants underlying X-linked intellectual disability disrupt protein function via distinct mechanisms.

Protein ubiquitylation regulates key biological processes including transcription. This is exemplified by the E3 ubiquitin ligase RNF12/RLIM, which controls developmental gene expression by ubiquitylating the REX1 transcription factor and is mutated in an X-linked intellectual disability disorder. However, the precise mechanisms by which ubiquitylation drives specific transcriptional responses are not known. Here, we show that RNF12 is recruited to specific genomic locations via a consensus sequence motif, which enables co-localisation with REX1 substrate at gene promoters. Surprisingly, RNF12 chromatin recruitment is achieved via a non-catalytic basic region and comprises a previously unappreciated N-terminal autoinhibitory mechanism. Furthermore, RNF12 chromatin targeting is critical for REX1 ubiquitylation and downstream RNF12-dependent gene regulation. Our results demonstrate a key role for chromatin in regulation of the RNF12-REX1 axis and provide insight into mechanisms by which protein ubiquitylation enables programming of gene expression.

Chromatin targeting of the RNF12/RLIM E3 ubiquitin ligase controls transcriptional responses.

Tonne-Kalscheuer syndrome (TOKAS) is a recessive X-linked multiple congenital anomaly disorder caused by  variations. Of the 41 patients reported, only 7 antenatal cases were described.

Article	Year
Therapeutic validation and targeting of signalling networks that are dysregulated in intellectual disability. The FEBS journal\| PubMed ID: 35212144	2023
variants underlying X-linked intellectual disability disrupt protein function via distinct mechanisms. Life science alliance\| PubMed ID: 38182161	2024
Chromatin targeting of the RNF12/RLIM E3 ubiquitin ligase controls transcriptional responses. Life science alliance\| PubMed ID: 38199845	2024
Extending the clinical spectrum of X-linked Tonne-Kalscheuer syndrome (TOKAS): new insights from the fetal perspective. Journal of medical genetics\| PubMed ID: 38849204	2024

Francisco Bustos

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