A certain proportion of patients with Mendelian diseases are overlooked, although substantial technical advances in molecular genetics have been achieved. Massively parallel sequencing (MPS) increasingly identifies genetic variants of unknown significance, which may remain clinically unhelpful. Furthermore, difficult niches in the genome exist, which cannot be solved by standard MPS. In the reported family autosomal dominant kidney disease leading to renal failure in middle adulthood runs through the maternal and paternal family. Comprehensive genetic analyses and customized functional evaluation solved the genetic etiologies: autosomal dominant polycystic kidney disease (ADPKD-PKD1, maternal) and autosomal dominant tubulointerstitial kidney disease (ADTKD-UMOD, paternal), with the index patient suffering from both diseases. The pathogenic variant in PKD1 (c.2180T>C, p.(Leu727Pro)) was not identified by exome sequencing (ES) but was unveiled by traditional long-range amplification protocols and whole genome sequencing. The ease of use of MPS increasingly tempts non-specialized genetic laboratories to perform broad analyses of numerous diseases, which in specific cases may worsen the quality of investigations, i.e. for the relatively frequent ADPKD.
Arif B. Ekici, K. Knaup, C. Schaeffer et al.· American Journal of Kidney D...· 0 citations
Variants in BRSK2, encoding brain specific kinase-2, have recently been associated with an autosomal dominant neurodevelopmental disorder (NDD). We have assembled 52 cases with heterozygous BRSK2 variants and variable neurodevelopmental phenotypes with frequent neuropsychiatric and behavioral symptoms. The variant spectrum included 15 different truncating variants, seven (potential) splice variants, three structural variants, and 12 different missense variants. Of the missense variants, seven were in the kinase domain, and the others in the UBA and the KA1 domain or outside domains. Variants occurred de novo in 19 cases and were inherited in 18. We utilized Drosophila melanogaster as a model and assessed viability and performed climbing and bang sensitivity assays upon knockdown of the fly orthologue sff or upon overexpression of wildtype or mutant human BRSK2. Pan-neuronal knockdown of sff resulted in impaired locomotor behavior and seizure susceptibility. Ubiquitous or pan-neuronal overexpression of human wildtype BRSK2 in Drosophila resulted in lethality or locomotor impairment, respectively, indicating toxicity. Overexpressing mutant BRSK2 did not or incompletely affect viability and locomotor behavior for six of seven tested kinase domain missense variants and one KA1 domain variant, indicating a (partial) loss-of-function effect. Interestingly, overexpressing BRSK2 with the remaining missense variant from the kinase domain and the two most C-terminal missense variants resulted in possible gain of function. Our findings further delineate the clinical and molecular spectrum of BRSK2-associated NDD and provide further insights into the role of BRSK2/sff in nervous system function and dysfunction.
Palak Singhal, Tzung-Chien Hsieh, Nadja Ehmke et al.· European Journal of Human Ge...· 0 citations