👤 Nasir Mukhtar

Indigenous chickens in tropical regions routinely survive high environmental temperatures (40-45 °C) that cause significant mortality and production loss in commercial breeds, yet the genetic mechanisms of thermotolerance remain poorly understood. This study integrated genome-wide selective scans across 14 geographically and climatically diverse chicken breeds with multi-tissue expression data, gene expression quantitative trait locus (eQTL) analysis, transcriptome-wide association study (TWAS), and cross-species phenome-wide association study (PheWAS) to validate candidate genes. We identified 25 high-confidence genes under selection, with ATP1A1, PLCB4, RYR2 and AKT3 forming a regulatory hub coordinating cardiovascular, calcium and survival signaling. These genes converge on interconnected adrenergic, calcium, and GnRH signaling pathways, with coordinated expression across heart, hypothalamus, and liver forming an integrated thermoregulatory axis. The eQTL integration analysis using ChickenGTEx data identified 359 tissue-specific cis-eQTLs in selected regions. Additionally, TWAS analysis linked ATP1A1 to 145 gene-trait associations across 13 tissues and 14 trait categories (hepatic regulation, β = -2.13, p = 4.21 × 10⁻¹²), and cross-species PheWAS validated conserved roles in cardiovascular function (RYR2, resting heart rate p = 4.9 × 10⁻¹²), and ionic homeostasis (ATP1A1, chloride p = 1.18 × 10⁻³). In parallel, we also identified robust genomic signatures of domestication in classic candidate genes (TSHR, TBC1D1, BDNF), highlighting how initial separation from Red Jungle Fowl and subsequent adaptation to diverse climates have shaped the genetic and physiological diversity of the domesticated chicken. Collectively, our results reveal an integrated cardio-neuroendocrine calcium network driving heat adaptation, providing potential targets for breeding heat-tolerant chickens. Show less

Germline pathogenic variants in checkpoint kinase 2 (CHEK2) are associated with a moderately increased risk of breast cancer (BC). The spectrum of clinicopathologic features and genetics of these tumors has not been fully established. We characterized the histopathologic and clinicopathologic features of 44 CHEK2-associated BCs from 35 women, and assessed responses to neoadjuvant chemotherapy. A subset of cases (n = 23) was additionally analyzed using targeted next-generation DNA sequencing (NGS). Most (94%, 33/35) patients were heterozygous carriers for germline CHEK2 variants, and 40% had the c.1100delC allele. Two patients were homozygous, and five had additional germline pathogenic variants in ATM (2), PALB2 (1), RAD50 (1), or MUTYH (1). CHEK2-associated BCs occurred in younger women (median age 45 years, range 25-75) and were often multifocal (20%) or bilateral (11%). Most (86%, 38/44) were invasive ductal carcinomas of no special type (IDC-NST). Almost all (95%, 41/43) BCs were ER + (79% ER + HER2-, 16% ER + HER2 + , 5% ER-HER2 +), and most (69%) were luminal B. Nottingham grade, proliferation index, and results of multiparametric molecular testing were heterogeneous. Biallelic CHEK2 alteration with loss of heterozygosity was identified in most BCs (57%, 13/23) by NGS. Additional recurrent alterations included GATA3 (26%), PIK3CA (226%), CCND1 (22%), FGFR1 (22%), ERBB2 (17%), ZNF703 (17%), TP53 (9%), and PPM1D (9%), among others. Responses to neoadjuvant chemotherapy were variable, but few patients (21%, 3/14) achieved pathologic complete response. Most patients (85%) were without evidence of disease at time of study (n = 34). Five patients (15%) developed distant metastasis, and one (3%) died (mean follow-up 50 months). Almost all CHEK2-associated BCs were ER + IDC-NST, with most classified as luminal B with or without HER2 overexpression. NGS supported the luminal-like phenotype and confirmed CHEK2 as an oncogenic driver in the majority of cases. Responses to neoadjuvant chemotherapy were variable but mostly incomplete. Show less