Biology subjects

Massrali, A.

Publications and source records attributed to Massrali, A..

3 recordsLinked to original sources

bioRxiv2026

Assessing the impact of mono- and bi-allelic deletions in NRXN1 on synaptic function

Neurexin 1 (NRXN1) is an adhesion protein involved in synapse development and function. Mutations in NRXN1 are strongly linked with neurodevelopmental and psychiatric conditions. Mono-allelic NRXN1 mutations are associated with autistic traits, with increased likelihood of co-occurring intellectual disability. However, mono-allelic mutations have variable penetrance and occur in individuals without neurodevelopmental phenotypes. Conversely, bi-allelic mutations, though rarer, are associated with more stable penetrance and severe neurodevelopmental phenotypes. Human induced pluripotent stem cells (iPSC) have been used to study how mutations in NRXN1 impacts its function, with most studies focusing on monoallelic mutations. In this study, we systematically compared monoallelic and biallelic mutations in NRXN1, characterising their effects on molecular, synaptic, and functional phenotypes. Using CRISPR-Cas9, we introduced indels in NRXN1 exon 19, in an iPSC line containing inducible NGN2. These edits caused either mono-allelic or compound bi-allelic frameshift mutations. iPSCs containing either mutation robustly generated glutamatergic neurons, but these neurons displayed reduced expression of major NRXN1 isoforms. Transcriptomic profiling revealed modest gene expression changes in mono-allelic mutant neurons, whereas bi-allelic mutants exhibited extensive dysregulation of gene networks associated with neuronal maturation and synaptic function. Furthermore, synaptic phenotypes were mild in mono-allelic mutants but pronounced in bi-allelic mutant neurons. Both mono-allelic and bi-allelic mutant neurons displayed alterations in neuronal network activity and reduced peak depolarisation responses to KCl stimulation. Together, these data demonstrate that NRXN1 exhibits gene-dosage sensitivity, with bi-allelic disruption of exon 19 unmasking molecular, synaptic, and functional phenotypes that are only modest in mono-allelic mutant neurons.

neuroscience↗

bioRxiv2024

Impact of intragenic NRXN1 deletions on early cortical development

BackgroundDeletions in NRXN1 are strongly associated with neurodevelopmental and psychiatric conditions. While exonic deletions are well-studied, intragenic deletions, particularly in intron 5, are less understood and generally consider benign. Recent studies show exonic deletions impact isoform diversity during neurodevelopment, affecting neurogenesis and neuronal function. However, whether intragenic deletions impact isoform expression and neurodevelopment remains underexplored. MethodsWe used hiPSCs from typically developing individuals (control) and those with NRXN1 intron 5 deletions to study neurodevelopment. HiPSCs were differentiated towards a cortical fate, with NRXN1 isoform expression, molecular differences, and neuronal morphology examined. ResultsWe observed distinct NRXN1 isoform expression dynamics during early neurodevelopment, with two expression peaks post-neuronal induction and NRXN1{beta} being most highly expressed. Both NRXN1 deletion and control lines showed similar acquisition of regional and cell fate identity, but significant differences in NRXN1 isoform expression were observed between deletion and control lines, and between deletion lines. RNA sequencing revealed genotype-dependent alterations, particularly in pathways related to synaptic function and neuronal morphology. Consistent with these findings, NRXN1 deletion lines exhibited altered dendrite outgrowth, with variations between deletion lines. ConclusionsOur results indicate a potential role for intron 5 in controlling NRXN1 isoform expression during neurodevelopment. Alterations in gene expression profiles, correlated with morphological changes, suggest a role for NRXN1 isoforms in shaping dendritic morphology. Molecular and cellular differences observed between lines with identical intronic deletions suggest that additional factors, such as genetic background or biological sex, may also play an important role in these phenotypes. Collectively, these findings indicate that NRXN1 intronic deletions are not benign, influencing isoform expression, cellular phenotypes, and neurodevelopment.

neuroscience↗

bioRxiv2018

Integrated genetic and methylomic analyses identify shared biology between autism and autistic traits

Previous studies have identified differences in DNA methylation in autistic individuals compared to neurotypical individuals. Yet, it is unclear if this extends to autistic traits - subclinical manifestation of autism features in the general population. Here, we investigate the association between DNA methylation at birth (cord blood), and scores on the Social and Communication Disorders Checklist (SCDC), a measure of autistic traits, in 701 8-year olds, by conducting a methylome-wide association study (MWAS) using DNA methylation data from cord-blood. Whilst did not identify significant loci demonstrating differential methylation, we observe a degree of overlap between the SCDC MWAS and post-mortem brain methylation signature in autism. Validating this, we observe an enrichment for genes that are dysregulated in the post-mortem autism brain. Finally, integrating genome-wide data from more than 40,000 individuals and mQTL maps from cord-blood, we demonstrate that mQTLs of CpGs associated with SCDC scores at different P-value thresholds are significantly shifted towards lower P-values in a GWAS for autism. We validate this using a GWAS of SCDC, and demonstrate a lack of enrichment in a GWAS of Alzheimers disease. Our results highlight the shared cross-tissue epigenetic architecture of autism and autistic traits, and demonstrate that mQTLs associated with methylation changes in childhood autistic traits are enriched for common genetic variants associated with autism and autistic traits.

genetics↗