Biology subjects

Murtaza, M.

Publications and source records attributed to Murtaza, M..

8 recordsLinked to original sources

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↗

bioRxiv2020

Genomic landscapes of canine splenic angiosarcoma (hemangiosarcoma) contain extensive heterogeneity within and between patients

Cancer genomic heterogeneity presents significant challenges for understanding oncogenic processes and for cancers clinical management. Variation in driver mutation frequency between patients with the same tumor type as well as within individual patients cancers can limit the power of mutations to serve as diagnostic, prognostic, and predictive biomarkers. We have characterized genomic heterogeneity between and within patients in canine splenic hemangiosarcoma (HSA), a common naturally occurring cancer in pet dogs that is similar to human angiosarcoma (AS). HSA is a clinically, physiologically, and genomically complex canine cancer that may serve as a valuable model for understanding the origin and clinical impact of cancer heterogeneity. We conducted a prospective collection of 52 splenic masses from 44 dogs (28 HSA, 15 benign masses, and 1 stromal sarcoma) presenting to emergency care with hemoperitoneum secondary to a ruptured splenic mass. Multi-platform genomic analysis included matched tumor/normal cancer gene panel and exome sequencing. We found candidate somatic cancer driver mutations in 14/28 (50%) HSAs. Among recurrent candidate driver mutations, TP53 was most commonly mutated (29%) followed by PIK3CA (14%), AKT1 (11%), and CDKN2AIP (11%). We also identified significant intratumoral genomic heterogeneity, consistent with a branched evolution model, through multi-region exome sequencing of three distinct tumor regions from selected primary splenic tumors. These data provide new perspective on the genomic landscape and comparative value of understanding HSA in pet dogs, particularly as a naturally occurring cancer bearing intratumoral heterogeneity.

cancer biology↗

bioRxiv2020

Feasibility and promise of circulating tumor DNA analysis in dogs with naturally-occurring sarcoma.

Comparative studies of naturally-occurring canine cancers have provided new insight into many areas of cancer research. The inclusion of pet dogs in the development and validation of circulating tumor DNA (ctDNA) diagnostics may be uniquely informative for human translation for many reasons, including: high incidence of certain spontaneous cancers, repeated access to blood and tumor from the same individuals during the course of disease progression, and molecular heterogeneity of naturally-occurring cancers in dogs. Here, we present a feasibility study of ctDNA analysis performed in 9 healthy dogs and 39 dogs with either benign or malignant splenic tumors (hemangiosarcoma) using shallow whole genome sequencing (sWGS) of cell-free DNA. To enable detection and quantification of ctDNA using sWGS, we adapted two informatic approaches and compared their performance for the canine genome. At presentation, mean ctDNA tumor fraction in dogs with malignant splenic tumors was 11.2%, significantly higher than dogs with benign lesions (3.2%; p 0.001), achieving an AUC of 0.84. ctDNA tumor fraction was 14.3% and 9.0% in dogs with metastatic and localized disease, respectively although this difference was not statistically significant (p 0.227). In paired analysis, ctDNA fraction decreased from 11.0% to 7.9% after resection of malignant tumors (p 0.047). Our results demonstrate that ctDNA analysis is feasible in dogs with hemangiosarcoma using a cost-effective approach such as sWGS. Future studies are underway to validate these findings, and further evaluate the role of ctDNA to assess burden of disease and treatment response during drug development.

genomics↗

bioRxiv2019

Crumbs 2 mediates ventricular layer remodelling to form the adult spinal cord central canal

In the spinal cord, the adult central canal forms through a poorly-understood process termed dorsal collapse that involves attrition and remodelling of the pseudostratified dorsal ventricular layer. Here we show, in mouse, that dorsal ventricular layer cells adjacent to midline Nestin(+) radial glia downregulate the apical polarity proteins Crumbs2 (CRB2) and aPKC and delaminate in a step-wise manner; concomitantly, Nestin(+) radial glial end-feet ratchet down, to repeat this process. Nestin(+) radial glia secrete a factor that promotes cell delamination. This activity is mimicked by a secreted variant of CRB2 (CRB2S), which is specifically expressed by dorsal midline Nestin(+) radial glia. In cultured cells, CRB2S associated with apical membranes and decreased cell cohesion. Analysis of Crb2F/F/Nestin-Cre+/- mice further confirmed an essential role for CRB2 in dorsal collapse. We propose a model in which CRB2S promotes the progressive attrition of the ventricular layer without loss of overall integrity. This novel mechanism may operate more widely to promote orderly progenitor delamination.

developmental biology↗

bioRxiv2019

Sub-nucleosomal organization in urine cell-free DNA

Cell-free DNA (cfDNA) in urine is a promising analyte for noninvasive diagnostics. However, urine cfDNA is highly fragmented and whether characteristics of these fragments reflect underlying genomic architecture is unknown. Here, we perform comprehensive characterization of fragmentation patterns in urine cfDNA. We show modal size and genome-wide distribution of urine cfDNA fragments are consistent with transient protection from degradation by stable intermediates of nucleosome disassembly. Genome-wide nucleosome occupancy and fragment sizes in urine cfDNA are informative of cell of origin and renal epithelial cells are amongst the highest contributors in urine. Compared to a nucleosome occupancy map based on control urine samples, we observe a higher fraction of fragments with aberrant ends in cancer patients, distinguishing cancer samples with an area under the curve of 0.89. Our results demonstrate sub-nucleosomal organization in urine cfDNA and are proof-of-principle that genome-wide fragmentation analysis of urine cfDNA can enable cancer diagnostics.

genomics↗

bioRxiv2019

Identification of frequent activating HER2 mutations in primary canine pulmonary adenocarcinoma

Naturally occurring primary canine lung cancers are aggressive malignancies that are increasingly common in pet dogs. They share clinicopathologic features with human lung cancers in never-smokers, but their genetic underpinnings are unknown. Through multi-platform sequencing of 88 primary canine lung tumors or cell lines, we discovered somatic, coding HER2 (ERRB2) point mutations in 38% of canine pulmonary adenocarcinomas (cPAC, 28/74), but none in adenosquamous (cPASC, 0/11) or squamous cell (cPSCC, 0/3) carcinomas. In cPASC, PTEN was the most frequently mutated gene (18%) while one case each bore likely pathogenic HRAS, KRAS, EGFR, MET, TP53, or VHL somatic mutations. In cPSCC, no recurrently mutated genes were identified, but individual somatic coding mutations were found in BRAF and PTPN11. In cPAC, we also identified recurrent somatic mutation of TP53 (13.5%), SMAD4 (5.4%), PTEN (4.1%), and VHL (2.7%). cPACs assessed by exome sequencing displayed a low somatic mutation burden (median 64 point mutations, 19 focal copy number variants, and 1 translocation). The majority (93%) of HER2 mutations were hotspot V659E transmembrane domain (TMD) mutations comparable to activating mutations at this same site in human cancer. Other HER2 mutations identified in this study were located in the extracellular domain and TMD. HER2V659E was detected in the plasma of 33% (2/6) of dogs with localized HER2V659E tumors. HER2V659E correlated with constitutive phosphorylation of AKT in cPAC cell lines and HER2V659E lines displayed hypersensitivity to the HER2 inhibitors lapatinib and neratinib relative to HER2-wild-type cell lines. These findings have translational and comparative relevance for lung cancer and HER2 inhibition.

cancer biology↗

bioRxiv2018

Detection of residual disease after neoadjuvant therapy in breast cancer using personalized circulating tumor DNA analysis

Accurate detection of minimal residual disease (MRD) can guide individualized management of early stage cancer patients, but current diagnostic approaches lack adequate sensitivity. Circulating tumor DNA (ctDNA) analysis has shown promise for recurrence monitoring but MRD detection immediately after neoadjuvant therapy or surgical resection has remained challenging. We have developed TARgeted DIgital Sequencing (TARDIS) to simultaneously analyze multiple patient-specific cancer mutations in plasma and improve sensitivity for minute quantities of residual tumor DNA. In 77 reference samples at 0.03%-1% mutant allele fraction (AF), we observed 93.5% sensitivity. Using TARDIS, we analyzed ctDNA in 34 samples from 13 patients with stage II/III breast cancer treated with neoadjuvant therapy. Prior to treatment, we detected ctDNA in 12/12 patients at 0.002%-1.04% AF (0.040% median). After completion of neoadjuvant therapy, we detected ctDNA in 7/8 patients with residual disease observed at surgery and in 1/5 patients with pathological complete response (odds ratio, 18.5, Fishers exact p=0.032). These results demonstrate high accuracy for a personalized blood test to detect residual disease after neoadjuvant therapy. With additional clinical validation, TARDIS could identify patients with molecular complete response after neoadjuvant therapy who may be candidates for nonoperative management.\n\nOne Sentence SummaryA personalized ctDNA test achieves high accuracy for residual disease.

genomics↗

bioRxiv2017

Evaluation of pre-analytical factors affecting plasma DNA analysis

Pre-analytical factors can significantly affect circulating cell-free DNA (cfDNA) analysis. However, there are few robust methods to rapidly assess sample quality and the impact of pre-analytical processing. To address this gap and to evaluate effects of DNA extraction methods and blood collection tubes on cfDNA yield and fragment size, we developed a multiplexed droplet digital PCR (ddPCR) assay with 5 short and 4 long amplicons targeting single copy genomic loci (mean amplicon size: 71 bp and 471 bp respectively). Using this assay, we compared performance of 7 cfDNA extraction kits and found cfDNA yield and fragment size varies significantly between them. We also compared 3 blood collection protocols used to collect plasma samples from 23 healthy volunteers (EDTA tubes processed within 1 hour and Cell-free DNA BCT tubes at ambient temperature processed within 24 hours and 72 hours of collection). To assess whether cell-stabilizing preservative in BCT tubes introduced noise in cfDNA, we performed digital targeted sequencing. We found no significant differences in cfDNA yield, fragment size and background sequencing noise between these protocols. In 219 clinical samples tested for quality using the ddPCR assay, cfDNA fragment size was significantly shorter in plasma samples immediately processed for ctDNA analysis compared to archived samples, suggesting background DNA contributed by lysed peripheral blood cells. In summary, we describe a multiplexed ddPCR approach that enables cfDNA quality assessment and could inform the design of future circulating tumor DNA studies.\n\nGene namesNone

genomics↗