👤 Jan Verheijen

To determine the prevalence, penetrance, and disease expression of cardiomyopathy-related genetic variants in an unselected, richly phenotyped Mayo Clinic population in the setting of preemptive sequencing, with return of incidental findings following the American College of Medical Genetics and Genomics recommendations. We analyzed a quaternary medical center-based biobank cohort (n=983) for reportable variants in 15 cardiomyopathy genes. Prioritization of genetic variants was performed using an internally developed pipeline to identify potentially reportable variants. Prioritized variants were then manually curated. The correlation of likely pathogenic/pathogenic (LP/P) variants with clinical phenotypes and outcomes was established. Artificial intelligence-enabled electrocardiographic predictions of reduced left ventricular ejection fraction and hypertrophic cardiomyopathy were applied to genotype-positive (G+) participants. Of the 983 patients, 11 (1%) were G+, with 11 LP/P variants found in the MYBPC3, DSG2, MYH7, DSP, and PKP2 genes. All G+ participants underwent electrocardiography, and 10 (90%) underwent echocardiography. Most patients (10 [90%]) did not have a prior diagnosis of cardiomyopathy. Definitive disease penetrance (heart failure or cardiomyopathy) was present in 4 (36%), while 3 (27%) had possible penetrance (structural heart disease identified by echocardiography). Arrhythmias and/or cardiac conduction disease was present in 4 of 11 G+ individuals (36%). Artificial intelligence-electrocardiography was positive for hypertrophic cardiomyopathy or reduced left ventricular ejection fraction in 5 of the G+ participants (45%), of whom 4 (80%) had definitive or possible disease penetrance. Cardiomyopathy-associated LP/P variants are present in a small subset of a quaternary medical center population, and disease penetrance in G+ individuals is high in the form of cardiac structural abnormalities and heart failure. Show less

The increasing pace of gene discovery in the last decade has brought a major change in the way the genetic causes of brain malformations are being diagnosed. Unbiased genomic screening has gained the first place in the diagnostic protocol of a child with congenital (brain) anomalies and the detected variants are matched with the phenotypic presentation afterwards. This process is defined as "reverse phenotyping". Screening of DNA, through copy number variant analysis of microarrays and analysis of exome data on different platforms, obtained from the index patient and both parents has become a routine approach in many centers worldwide. Clinicians are used to multidisciplinary team interaction in patient care and disease management and this explains why the majority of research that has led to the discovery of new genetic disorders nowadays proceeds from clinical observations to genomic analysis and to data exchange facilitated by open access sharing databases. However, the relevance of multidisciplinary team interaction has not been object of systematic research in the field of brain malformations. This review will illustrate some examples of how diagnostically driven questions through multidisciplinary interaction, among clinical and preclinical disciplines, can be successful in the discovery of new genes related to brain malformations. The first example illustrates the setting of interaction among neurologists, geneticists and neuro-radiologists. The second illustrates the importance of interaction among clinical dysmorphologists for pattern recognition of syndromes with multiple congenital anomalies. The third example shows how fruitful it can be to step out of the "clinical comfort zone", and interact with basic scientists in applying emerging technologies to solve the diagnostic puzzles. Show less

To date, mutations in 15 actin- or microtubule-associated genes have been associated with the cortical malformation lissencephaly and variable brainstem hypoplasia. During a multicenter review, we recognized a rare lissencephaly variant with a complex brainstem malformation in three unrelated children. We searched our large brain-malformation databases and found another five children with this malformation (as well as one with a less severe variant), analyzed available whole-exome or -genome sequencing data, and tested ciliogenesis in two affected individuals. The brain malformation comprised posterior predominant lissencephaly and midline crossing defects consisting of absent anterior commissure and a striking W-shaped brainstem malformation caused by small or absent pontine crossing fibers. We discovered heterozygous de novo missense variants or an in-frame deletion involving highly conserved zinc-binding residues within the GAR domain of MACF1 in the first eight subjects. We studied cilium formation and found a higher proportion of mutant cells with short cilia than of control cells with short cilia. A ninth child had similar lissencephaly but only subtle brainstem dysplasia associated with a heterozygous de novo missense variant in the spectrin repeat domain of MACF1. Thus, we report variants of the microtubule-binding GAR domain of MACF1 as the cause of a distinctive and most likely pathognomonic brain malformation. A gain-of-function or dominant-negative mechanism appears likely given that many heterozygous mutations leading to protein truncation are included in the ExAC Browser. However, three de novo variants in MACF1 have been observed in large schizophrenia cohorts. Show less