Recommendations for clinical interpretation of variants found in non-coding regions of the genome.

BACKGROUND: The majority of clinical genetic testing focuses almost exclusively on regions of the genome that directly encode proteins. The important role of variants in non-coding regions in penetrant disease is, however, increasingly being demonstrated, and the use of whole genome sequencing in clinical diagnostic settings is rising across a large range of genetic disorders. Despite this, there is no existing guidance on how current guidelines designed primarily for variants in protein-coding regions should be adapted for variants identified in other genomic contexts. METHODS: We convened a panel of nine clinical and research scientists with wide-ranging expertise in clinical variant interpretation, with specific experience in variants within non-coding regions. This panel discussed and refined an initial draft of the guidelines which were then extensively tested and reviewed by external groups. RESULTS: We discuss considerations specifically for variants in non-coding regions of the genome. We outline how to define candidate regulatory elements, highlight examples of mechanisms through which non-coding region variants can lead to penetrant monogenic disease, and outline how existing guidelines can be adapted for the interpretation of these variants. CONCLUSIONS: These recommendations aim to increase the number and range of non-coding region variants that can be clinically interpreted, which, together with a compatible phenotype, can lead to new diagnoses and catalyse the discovery of novel disease mechanisms.

Correction: KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants.

PURPOSE: Pathogenic variants in KAT6A have recently been identified as a cause of syndromic developmental delay. Within 2 years, the number of patients identified with pathogenic KAT6A variants has rapidly expanded and the full extent and variability of the clinical phenotype has not been reported. METHODS: We obtained data for patients with KAT6A pathogenic variants through three sources: treating clinicians, an online family survey distributed through social media, and a literature review. RESULTS: We identified 52 unreported cases, bringing the total number of published cases to 76. Our results expand the genotypic spectrum of pathogenic variants to include missense and splicing mutations. We functionally validated a pathogenic splice-site variant and identified a likely hotspot location for de novo missense variants. The majority of clinical features in KAT6A syndrome have highly variable penetrance. For core features such as intellectual disability, speech delay, microcephaly, cardiac anomalies, and gastrointestinal complications, genotype- phenotype correlations show that late-truncating pathogenic variants (exons 16-17) are significantly more prevalent. We highlight novel associations, including an increased risk of gastrointestinal obstruction. CONCLUSION: Our data expand the genotypic and phenotypic spectrum for individuals with genetic pathogenic variants in KAT6A and we outline appropriate clinical management.

Functional mRNA analysis reveals aberrant splicing caused by novel intronic mutation in WDR45 in NBIA patient.

WDR45 gene-associated neurodegeneration with brain iron accumulation (NBIA), referred to as beta-propeller protein-associated neurodegeneration (BPAN), is a rare disorder that presents with a very nonspecific clinical phenotype in children constituting global developmental delay. This case report illustrates the power of a combination of trio exome sequencing, in silico splicing analysis, and mRNA analysis to provide sufficient evidence for pathogenicity of a relatively intronic variant in WDR45, and in so doing, find a genetic diagnosis for a 6-year-old patient with developmental delay and seizures, a diagnosis which may otherwise have only been found once the characteristic MRI patterns of the disease became more obvious in young adulthood.

Evidence for different, host-dependent functioning of Rx against both wild-type and recombinant Pepino mosaic virus.

The potato Rx gene provides resistance against Pepino mosaic virus (PepMV) in tomato; however, recent work has suggested that the resistance conferred may not be durable. Resistance breaking can probably be attributed to multiple mutations observed to accumulate in the capsid protein (CP) region of resistance-breaking isolates, but this has not been confirmed through directed manipulation of an infectious PepMV clone. The present work describes the introduction of two specific mutations, A-T78 and A-T114, into the coat protein minimal elicitor region of an Rx-controlled PepMV isolate of the EU genotype. Enzyme-linked immunosorbent assay (ELISA) and phenotypic evaluation were conducted in three Rx-expressing and wild-type solanaceous hosts: Nicotiana benthamiana, Nicotiana tabacum and Solanum lycopersicum. Mutation A-T78 alone was sufficient to confer Rx-breaking activity in N. benthamiana and S. lycopersicum, whereas mutation A-T114 was found to be associated, in most cases, with a secondary A-D100 mutation to break Rx-mediated resistance in S. lycopersicum. These results suggest that the need for a second, fitness-restoring mutation may be dependent on the PepMV mutant under consideration. Both mutations conferred Rx breaking in S. lycopersicum, whereas neither conferred Rx breaking in N. tabacum and only A-T78 allowed Rx breaking in N. benthamiana, suggesting that Rx may function in a different manner depending on the genetic background in which it is present.

A pathogenicity determinant maps to the N-terminal coat protein region of the Pepino mosaic virus genome.

Pepino mosaic virus (PepMV) poses a worldwide threat to the tomato industry. Considerable differences at the genetic level allow for the distinction of four main genotypic clusters; however, the basis of the phenotypic outcome is difficult to elucidate. This work reports the generation of wild-type PepMV infectious clones of both EU (mild) and CH2 (aggressive) genotypes, from which chimeric infectious clones were created. Phenotypic analysis in three solanaceous hosts, Nicotiana benthamiana, Datura stramonium and Solanum lycopersicum, indicated that a PepMV pathogenicity determinant mapped to the 3'-terminal region of the genome. Increased aggression was only observed in N. benthamiana, showing that this factor is host specific. The determinant was localized to amino acids 11-26 of the N-terminal coat protein (CP) region; this is the first report of this region functioning as a virulence factor in PepMV.