Monaghan, Kristin G.

AbstractCSNK2B has recently been implicated as a disease gene for neurodevelopmental disability (NDD) and epilepsy. Information about developmental outcomes has been limited by the young age and short follow‐up for many of the previously reported cases, and further delineation of the spectrum of associated phenotypes is needed. We present 25 new patients with variants in CSNK2B and refine the associated NDD and epilepsy phenotypes. CSNK2B variants were identified by research or clinical exome sequencing, and investigators from different centers were connected via GeneMatcher. Most individuals had developmental delay and generalized epilepsy with onset in the first 2 years. However, we found a broad spectrum of phenotypic severity, ranging from early normal development with pharmacoresponsive seizures to profound intellectual disability with intractable epilepsy and recurrent refractory status epilepticus. These findings suggest that CSNK2B should be considered in the diagnostic evaluation of patients with a broad range of NDD with treatable or intractable seizures.

Abstract Context. —Bioelectronic sensors, which combine microchip and biological components, are an emerging technology in clinical diagnostic testing. An electronic detection platform using DNA biochip technology (eSensor) is under development for molecular diagnostic applications. Owing to the novelty of these devices, demonstrations of their successful use in practical diagnostic applications are limited. Objective. —To assess the performance of the eSensor bioelectronic method in the validation of 6 Epstein-Barr virus–transformed blood lymphocyte cell lines with clinically important mutations for use as sources of genetic material for positive controls in clinical molecular genetic testing. Two cell lines carry mutations in the CFTR gene (cystic fibrosis), and 4 carry mutations in the HFE gene (hereditary hemochromatosis). Design. —Samples from each cell line were sent for genotype determination to 6 different molecular genetic testing facilities, including the laboratory developing the DNA biochips. In addition to the bioelectronic method, at least 3 different molecular diagnostic methods were used in the analysis of each cell line. Detailed data were collected from the DNA biochip output, and the genetic results were compared with those obtained using the more established methods. Results. —We report the successful use of 2 applications of the bioelectronic platform, one for detection of CFTR mutations and the other for detection of HFE mutations. In all cases, the results obtained with the DNA biochip were in concordance with those reported for the other methods. Electronic signal output from the DNA biochips clearly differentiated between mutated and wild-type alleles. This is the first report of the use of the cystic fibrosis detection platform. Conclusions. —Bioelectronic sensors for the detection of disease-causing mutations performed well when used in a “real-life” situation, in this case, a validation study of positive control blood lymphocyte cell lines with mutations of public health importance. This study illustrates the practical potential of emerging bioelectronic DNA detection technologies for use in current molecular diagnostic applications.

Germ line mutations in H3F3A and H3F3B cause a previously unidentified neurodevelopmental syndrome.

Abstract Asparagine‐linked glycosylation 13 homolog ( ALG13 ) encodes a nonredundant, highly conserved, X‐linked uridine diphosphate (UDP)‐ N ‐acetylglucosaminyltransferase required for the synthesis of lipid linked oligosaccharide precursor and proper N‐linked glycosylation. De novo variants in ALG13 underlie a form of early infantile epileptic encephalopathy known as EIEE36, but given its essential role in glycosylation, it is also considered a congenital disorder of glycosylation (CDG), ALG13‐CDG. Twenty‐four previously reported ALG13‐CDG cases had de novo variants, but surprisingly, unlike most forms of CDG, ALG13‐CDG did not show the anticipated glycosylation defects, typically detected by altered transferrin glycosylation. Structural homology modeling of two recurrent de novo variants, p.A81T and p.N107S, suggests both are likely to impact the function of ALG13. Using a corresponding ALG13‐deficient yeast strain, we show that expressing yeast ALG13 with either of the highly conserved hotspot variants rescues the observed growth defect, but not its glycosylation abnormality. We present molecular and clinical data on 29 previously unreported individuals with de novo variants in ALG13 . This more than doubles the number of known cases. A key finding is that a vast majority of the individuals presents with West syndrome, a feature shared with other CDG types. Among these, the initial epileptic spasms best responded to adrenocorticotropic hormone or prednisolone, while clobazam and felbamate showed promise for continued epilepsy treatment. A ketogenic diet seems to play an important role in the treatment of these individuals.