POLR1A variants underlie phenotypic heterogeneity in craniofacial, neural, and cardiac anomalies

Heterozygous pathogenic variants in POLR1A, which encodes the largest subunit of RNA Polymerase I, were previously identified as the cause of acrofacial dysostosis, Cincinnati-type. The predominant phenotypes observed in the cohort of 3 individuals were craniofacial anomalies reminiscent of Treacher Collins syndrome. We subsequently identified 17 additional individuals with 12 unique heterozygous variants in POLR1A and observed numerous additional phenotypes including neurodevelopmental abnormalities and structural cardiac defects, in combination with highly prevalent craniofacial anomalies and variable limb defects. To understand the pathogenesis of this pleiotropy, we modeled an allelic series of POLR1A variants in vitro and in vivo. In vitro assessments demonstrate variable effects of individual pathogenic variants on ribosomal RNA synthesis and nucleolar morphology, which supports the possibility of variant-specific phenotypic effects in affected individuals. To further explore variant-specific effects in vivo, we used CRISPR-Cas9 gene editing to recapitulate two human variants in mice. Additionally, spatiotemporal requirements for Polr1a in developmental lineages contributing to congenital anomalies in affected individuals were examined via conditional mutagenesis in neural crest cells (face and heart), the second heart field (cardiac outflow tract and right ventricle), and forebrain precursors in mice. Consistent with its ubiquitous role in the essential function of ribosome biogenesis, we observed that loss of Polr1a in any of these lineages causes cell-autonomous apoptosis resulting in embryonic malformations. Altogether, our work greatly expands the phenotype of human POLR1A-related disorders and demonstrates variant-specific effects that provide insights into the underlying pathogenesis of ribosomopathies.

Genetics and Precision Medicine: Heritable Thoracic Aortic Disease

Heritable thoracic aortic disease (HTAD) can have life-threatening consequences if not diagnosed early. Affected individuals and at-risk family members benefit from both cardiology and genetic evaluations, including genetic testing. Important information can be obtained through family history, medical history, and genetic testing to help guide management and assess risk. A genetic diagnosis can guide cardiovascular management (type and frequency of vascular imaging, timing of surgical intervention), risk assessment for arterial aneurysm/dissection, evaluation of nonvascular features, and familial testing.

Genetic Counselors: An Important Resource for Families following a Young Sudden Cardiac Death

Sudden cardiac death is a tragic result of a number of cardiovascular diseases. While the majority of sudden cardiac death cases are in older individuals with coronary artery disease, victims also include younger people (those less than 40 years old). At least 40% of cases of young sudden death are attributable to genetic causes, including diagnoses such as long QT syndrome and hypertrophic cardiomyopathy. In 50% of young sudden death cases, there are no warning signs or family history of sudden death. These young sudden deaths are a tragedy for families and in many cases are devastating for communities as well. Awareness is spreading among medical examiners and cardiologists on how to assess and treat these families but few healthcare providers see cases routinely. The combination of an unexpected death and the burden of potentially having a genetic disease themselves leaves family members in a vulnerable and often overwhelming position. Genetic counselors, particularly those who specialize in cardiovascular disease, are uniquely qualified to help surviving family members navigate the medical and psychosocial issues present in these cases.

National Association of Medical Examiners Position Paper: Retaining Postmortem Samples for Genetic Testing

Sudden unexpected death is typically diagnosed in infants, children, teenagers, and young adults following completion of an autopsy that fails to identify a cause of death or when autopsy suggests a potentially genetic cause of death in an individual less than 40, such as cardiomyopathy or aneurysm. Such deaths may be a result of genetic abnormalities that are unable to be diagnosed by gross or microscopic inspection, but may be detectable by molecular studies. Unfortunately, the ability to perform postmortem genetic testing is frequently hindered by lack of an appropriate specimen following completion of an autopsy. This paper provides recommendations developed by the National Association of Medical Examiners with the assistance of genetic counselors. The recommendations establish procedures to facilitate postmortem genetic testing and DNA banking by health care professionals assisting families who have experienced sudden death in young relatives by clarifying proper sample acquisition and storage. Additionally, recommendations for discussion with surviving family members and test planning are provided. The objective of these recommendations is to ensure that postmortem samples suitable for DNA banking are retained, allowing at risk family members improved detection of potentially treatable genetic diseases.

Glycogen storage disease type III-hepatocellular carcinoma a long-term complication?

BACKGROUND/AIMS

Glycogen storage disease III (GSD III) is caused by a deficiency of glycogen-debranching enzyme which causes an incomplete glycogenolysis resulting in glycogen accumulation with abnormal structure (short outer chains resembling limit dextrin) in liver and muscle. Hepatic involvement is considered mild, self-limiting and improves with age. With increased survival, a few cases of liver cirrhosis and hepatocellular carcinoma (HCC) have been reported.

METHODS

A systematic review of 45 cases of GSD III at our center (20 months to 67 years of age) was reviewed for HCC, 2 patients were identified. A literature review of HCC in GSD III was performed and findings compared to our patients.

CONCLUSIONS

GSD III patients are at risk for developing HCC. Cirrhosis was present in all cases and appears to be responsible for HCC transformation There are no reliable biomarkers to monitor for HCC in GSD III. Systematic evaluation of liver disease needs be continued in all patients, despite lack of symptoms. Development of guidelines to allow for systematic review and microarray studies are needed to better delineate the etiology of the hepatocellular carcinoma in patients with GSD III.