Biology subjects

Nassir, N.

Publications and source records attributed to Nassir, N..

7 recordsLinked to original sources

bioRxiv2026

Phenotype Dependent Segregation of a Novel EPS8 Variant for Hearing Loss and an HPDL Variant for Neurodevelopmental Disorders in a Complex Consanguineous Family

Consanguinity increases the risk of autosomal recessive disorders and may result in the co-segregation of multiple pathogenic variants within the same family. Although most affected families are explained by a single genetic diagnosis, multilocus pathogenic variation can produce complex and overlapping clinical phenotypes. We investigated a consanguineous Pakistani family with three affected siblings, including dizygotic twins presenting with neurodevelopmental disorder and hearing loss, using detailed clinical evaluation, long-read whole-genome sequencing, bulk transcriptomics, protein profiling, and segregation analysis to determine the underlying molecular diagnoses. One sibling presented with isolated non-syndromic hearing loss, whereas the dizygotic twins exhibited severe neurodevelopmental impairment characterized by global developmental delay, spastic quadriplegic cerebral palsy, microcephaly, and white matter abnormalities. Long-read whole-genome sequencing identified a homozygous start-loss variant in HPDL (c.3G>C) in both twins, consistent with HPDL-related neurodevelopmental disorder with progressive spasticity and brain white matter abnormalities (NEDSWMA). In addition, a novel homozygous nonsense variant in EPS8 (c.1294C>T) was identified in one twin and the sibling with isolated hearing loss, explaining the auditory phenotype. Long-read transcriptomic analysis demonstrated absence of detectable EPS8 transcripts in both individuals homozygous for the nonsense variant, providing transcript-level evidence consistent with a loss-of-function mechanism. Genome-wide comprehensive proteomic profiling (SomaScan) identified distinct protein abundance profiles across family members, with the most pronounced alterations observed in the twins affected by HPDL-related neurodevelopmental disease, particularly the individual harboring pathogenic variants in both EPS8 and HPDL. This study expands the mutational spectrum of EPS8 and highlights the independent segregation of two autosomal recessive disorders within the complex consanguineous family, resulting in distinct and blended phenotypes.

genetics↗

bioRxiv2026

Isoform-Resolved Genetic Architecture of Epilepsy and SUDEP Reveals Divergent Brain and Heart Channelopathy Signatures

Sudden unexpected death in epilepsy (SUDEP) is the most devastating complication of epilepsy, yet the molecular features distinguishing individuals at risk remain poorly defined. Although epilepsy and SUDEP share substantial genetic overlap, fatal outcomes may arise when shared risk genes are differentially deployed across neuronal and cardiac systems. Here, we identify tissue- and isoform-level regulation as a key determinant of divergence between epilepsy and SUDEP risk. We performed a large-scale integrated analysis of genetic variants reported in epilepsy and SUDEP across 419 sequencing-based studies encompassing 35,659 individuals, and quantified gene-level burden using a Bayesian Poisson-Gamma rate ratio framework. This analysis revealed preferential enrichment of genes related to cardiac electrophysiology and contractile function in SUDEP, whereas epilepsy was dominated by genes involved in neuronal excitability and synaptic signaling. To determine how shared genetic loci are deployed across tissues, we integrated GTEx-based tissue expression profiles with long-read single-cell transcriptomic datasets from human heart and brain to resolve isoform-level expression patterns. These analyses revealed pronounced tissue-specific transcript architectures. Cardiac-associated genes, including HCN4, KCNH2, KCNE1, MYH6, MYO18B, and ATP1A2, showed heart-restricted isoform expression, whereas neuronal genes such as ADGRV1, CACNA1A, GRIN2B, HCN1, HCN2, KCNA1, SCN1A, SCN2A, and SCN8A. Importantly, several shared genes exhibited tissue-partitioned isoform expression, with distinct transcript repertoires in heart and brain, particularly across pathways related to ion transport, signaling, metabolism, and structural organization. Consistent patterns were observed in iPSC-derived cardiomyocytes and neurons, indicating that lineage-dependent deployment of shared genes is preserved in controlled systems. Together, these findings suggest that tissue-specific isoform regulation provides a mechanistic basis linking shared epilepsy genetics to SUDEP susceptibility, whereby the same genetic loci contribute to neuronal dysfunction in epilepsy and to cardiac vulnerability in SUDEP. This positions SUDEP as a neuro-cardiac interface disorder shaped by isoform-level regulatory divergence.

genetics↗

bioRxiv2025

PanScan: A Tool for Tertiary Analysis of Human Pangenome Graphs

The genomic representation of populations across the globe is critical to ensuring a comprehensive and equitable human reference. Constructing a pangenome graph reference for different populations is the best approach to addressing local genomic diversities. Although major initiatives across continents are underway to construct pangenome graph references, the field lacks the necessary toolsets for tertiary analysis to characterize telomere-to-telomere (T2T) assemblies and the complexity of haplotypes. PanScan is a bioinformatics software package developed for human pangenome tertiary analysis. It includes multiple modules designed to detect duplicated gene sets from T2T assemblies, identify novel variants and sequences, as well as detect and visualize complex genomic regions through pangenome graph haplotype loops. We have used multiple pangenomes across different populations to assess the tertiary analysis and their accuracy. The tool is designed to streamline tertiary analysis and is compatible with multiple pangenome graph construction algorithms. PanScan is freely available on GitHub (https://github.com/CATG-Github/panscan), where users can provide human pangenome assemblies or VCF files as inputs for automated analyses through command-line operations on Linux systems. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=151 SRC="FIGDIR/small/651685v1_ufig1.gif" ALT="Figure 1"> View larger version (59K): org.highwire.dtl.DTLVardef@16cc212org.highwire.dtl.DTLVardef@13961d0org.highwire.dtl.DTLVardef@44d194org.highwire.dtl.DTLVardef@1b72aa_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioinformatics↗

bioRxiv2024

A draft Arab pangenome reference

Pangenomes represent a significant shift from relying on a single reference sequence to a robust set of assemblies, Arab populations remain significantly underrepresented; hence, we present the first Arab Pangenome Reference (APR) utilizing 53 individuals of diverse Arab ethnicities. We assembled nuclear and mitochondrial pangenomes using 35.27X high-fidelity long reads, 54.22X ultralong reads and 65.46X Hi-C reads yielded contiguous haplotype-phased de novo assemblies of exceptional quality, with an average N50 of 124.28 Mb. We discovered 111.96 million base pairs of novel euchromatic sequences absent from existing human pangenomes, the T2T-CHM13, GRCh38 reference human genomes, and other public datasets. We identified 8.94 million population-specific small variants and 235,195 structural variants within the Arab pangenome. We detected 883 gene duplications including 15.06% associated with recessive diseases and 1,436 bp of novel mitochondrial pangenome sequence. Our study provides a valuable resource for future genomic medicine initiatives in Arab population and other global populations.

genomics↗

bioRxiv2024

Horizon: CNV interpretation through rapid automated ACMG-aligned pathogenicity analysis

PurposeOur study assesses the Horizon model, a novel CNV classification tool developed in line with American College of Medical Genetics (ACMG) guidelines, to enhance the classification of pathogenicity in CNVs. MethodsHorizon utilizes a ranking-based algorithm, incorporating multiple proprietary databases and variant inheritance models as per ACMG standards. The models effectiveness was verified through Area Under the Curve (AUC) analyses on three datasets comprising 696 pathogenic inherited or de novo variants, as classified by clinical geneticists and several established tools. ResultsHorizon achieved an AUC of 0.97 in the discovery cohort, demonstrating high accuracy in CNV interpretation and proficiency in predicting pathogenicity. We observed an AUC of 0.87 in the de novo variant cohort and an overall AUC of 0.94 across all cohorts, surpassing tools like ClassifyCNV and AnnotSV. It showed particular effectiveness in interpreting duplication CNVs and the highest performance for CNVs sized 3-5 Mb. ConclusionThe Horizon model offers robust and accurate CNV interpretation, outperforming existing tools and aligning closely with clinical evaluations. Its comprehensive approach, integrating a range of genomic features and following ACMG guidelines, makes it a crucial tool in the genomic interpretation landscape, facilitating the rapid and accurate diagnosis of genetic disorders.

genomics↗

bioRxiv2023

Neuronal SNCA transcription during Lewy body formation

BackgroundMisfolded -synuclein (-syn) is believed to contribute to neurodegeneration in Lewy body disease (LBD) based on considerable evidence including a gene-dosage effect observed in relation to point mutations and multiplication of SNCA in familial Parkinsons disease. A contradictory concept proposes early loss of the physiological -syn as the major driver of neurodegeneration. There is a paucity of data on SNCA transcripts in various -syn immunoreactive cytopathologies. MethodsSNCA transcripts in neurons without and with various -syn immunoreactive cytopathologies in the substantia nigra and amygdala in LBD (n = 5) were evaluated using RNAscope combined with immunofluorescence for disease-associated -syn. Single-nucleus RNA sequencing was performed to elucidate cell-type specific SNCA expression in non-diseased frontal cortex (n = 3). ResultsSNCA transcripts in neurons with punctate -syn immunoreactivity were preserved both in the substantia nigra and amygdala but were reduced in neurons with compact -syn inclusions. Only single SNCA transcripts were detected in astrocytes with or without -syn immunoreactivity in the amygdala. Single-nucleus RNA sequencing revealed that excitatory and inhibitory neurons, oligodendrocyte progenitor cells, oligodendrocytes, and homeostatic microglia expressed SNCA transcripts, while expression was largely absent in astrocytes and microglia. ConclusionsThe preserved cellular SNCA expression in the more abundant non-Lewy body type -syn cytopathologies provides a pool for local protein production that can aggregate and serve as a seed for misfolded -syn. Successful segregation of disease-associated -syn is associated with the exhaustion of SNCA production in the terminal cytopathology, the Lewy body. Our observations support a therapeutic strategy incorporating a finely tuned dual approach targeting the elimination of misfolded -syn along with the reduction of the SNCA transcription to avoid feeding of pathological -syn seeding.

pathology↗

bioRxiv2019

A telomerase with novel non-canonical roles: TERT controls cellular aggregation and tissue size in Dictyostelium

Telomerase, particularly its main subunit, the reverse transcriptase, TERT, prevents DNA erosion during eukaryotic chromosomal replication, but also has poorly understood non-canonical functions. Here, in the model social amoeba Dictyostelium discoideum, we show that the protein encoded by tert has telomerase-like motifs and regulates, non-canonically, important developmental processes. Expression levels of wild-type (WT) tert were biphasic, peaking at 8 and 12 h post-starvation, aligning with developmental events, such as the initiation of streaming ([~]7 h) and mound formation ([~]10 h). In tert KO mutants, however, aggregation was delayed until 16 h. Large, irregular streams formed, then broke up, leading to small mounds. The mound-size defect was not induced when a KO mutant of countin (a master size-regulating gene) was treated with TERT inhibitors but anti-countin antibodies did rescue size in the tert KO. Further, conditioned medium from countin mutants failed to rescue size in the tert KO, but the converse experiment worked. These and additional observations indicate that TERT acts upstream of smlA/countin to regulate tissue size: (i) the observed expression levels of smlA and countin, being respectively lower and higher (than WT) in the tert KO; (ii) the levels of known size-regulation intermediates, glucose (low) and adenosine (high), in the tert mutant, and the size defects rescue by supplementing glucose or the adenosine-inhibitor, caffeine; (iii) the induction of the size defect in the WT by tert KO conditioned medium and TERT inhibitors. The tert KOs other defects (delayed aggregation, irregular streaming) were associated with changes to cAMP-regulated processes (e.g. chemotaxis, cAMP pulsing) and their regulatory factors (e.g. cAMP; acaA, carA expression). Overexpression of WT tert in the tert KO rescued these defects (and size), and restored a single cAMP signalling centre. Our results indicate that TERT acts in novel, non-canonical and upstream ways, regulating key developmental events in Dictyostelium. Author summaryWhen cells divide, their chromosomes are prone to shrinkage. This risk is reduced by an enzyme that repairs protective caps on each chromosome after cell division. This enzyme, telomerase, also has several other important but unrelated roles in human health. Most importantly, via one or other of its functions, both high and low levels of the enzyme can contribute to cancer. We have studied, for the first time, the roles played by telomerase in the life-cycle of the cellular slime mould, Dictyostelium discoideum, a model system with a rich history of helping us understand human biology. While we did not find any evidence of telomerase having the features typically needed to repair a chromosome, telomerase was necessary for many aspects of development. In forming the fruiting bodies that help Dictyostelium reproduce, a mutant that lacks telomerase miscalculates how big those bodies should be, and they end up being too small. Also, earlier, during an earlier stage, aggregation, the migration of cells that form each fruiting body is delayed and irregular. These results are significant because they show, for the first time, that a telomerase can influence cell migration and tissue size regulation, two processes involved in a wide range of cancers.

developmental biology↗