Functional characterization of a novel PBX1 de novo missense variant identified in a patient with syndromic congenital heart disease.

Pre-B cell leukemia factor 1 (PBX1) is an essential developmental transcription factor, mutations in which have recently been associated with CAKUTHED syndrome, characterized by multiple congenital defects including congenital heart disease (CHD). During analysis of a whole-exome-sequenced cohort of heterogeneous CHD patients, we identified a de novo missense variant, PBX1:c.551G>C p.R184P, in a patient with tetralogy of Fallot with absent pulmonary valve and extra-cardiac phenotypes. Functional analysis of this variant by creating a CRISPR-Cas9 gene-edited mouse model revealed multiple congenital anomalies. Congenital heart defects (persistent truncus arteriosus and ventricular septal defect), hypoplastic lungs, hypoplastic/ectopic kidneys, aplastic adrenal glands and spleen, as well as atretic trachea and palate defects were observed in the homozygous mutant embryos at multiple stages of development. We also observed developmental anomalies in a proportion of heterozygous embryos, suggestive of a dominant mode of inheritance. Analysis of gene expression and protein levels revealed that although Pbx1 transcripts are higher in homozygotes, amounts of PBX1 protein are significantly decreased. Here, we have presented the first functional model of a missense PBX1 variant and provided strong evidence that p.R184P is disease-causal. Our findings also expand the phenotypic spectrum associated with pathogenic PBX1 variants in both humans and mice.

Implementation and Evaluation of a National Multidisciplinary Kidney Genetics Clinic Network Over 10 Years.

Introduction: Diagnostic genomic sequencing is the emerging standard of care in nephrology. There is a growing need to scale up the implementation of genomic diagnostics nationally to improve patient outcomes. Methods: This pragmatic study provided genomic or genetic testing to patients with suspected monogenic kidney disease through a national network of kidney genetics clinics (KGCs). We sought to evaluate the experiences of implementing genomic diagnostics across Australia and associated diagnostic outcomes between 2013 and 2022. Results: We successfully established and expanded a nationwide network of 20 clinics as of 2022; concurrently developing laboratory, research, and education programs to scale the clinical application of genomics in nephrology. We report on an Australian cohort of 1506 kidney patients, of whom 1322 received their test results. We assessed barriers to implementation in the nephrology context, and where possible, applied real-time solutions to improve clinical processes over 10 years. Conclusion: Developing a multidisciplinary kidney genetics model across multiple health services nationally was highly successful. This model supported optimal care of individuals with monogenic kidney disease in an economically responsible way. It has continued to evolve with technological and service developments and is now set to scale further as genomic testing for kidney patients transitions to health care system funding.