Whole-exome sequencing in syndromic craniosynostosis increases diagnostic yield and identifies candidate genes in osteogenic signaling pathways

RNA Polymerase II activity control of gene expression and involvement in disease

Gene expression is dependent on RNA Polymerase II (Pol II) activity in eukaryotes. In addition to determining the rate of RNA synthesis for all protein coding genes, Pol II serves as a platform for the recruitment of factors and regulation of co-transcriptional events, from RNA processing to chromatin modification and remodeling. The transcriptome can be shaped by changes in Pol II kinetics affecting RNA synthesis itself or because of alterations to co-transcriptional events that are responsive to or coupled with transcription. Genetic, biochemical, and structural approaches to Pol II in model organisms have revealed critical insights into how Pol II works and the types of factors that regulate it. The complexity of Pol II regulation generally increases with organismal complexity. In this review, we describe fundamental aspects of how Pol II activity can shape gene expression, discuss recent advances in how Pol II elongation is regulated on genes, and how altered Pol II function is linked to human disease and aging.

Novel FOXP2 variant associated with speech and language dysfunction in a Chinese family and literature review

Since its initial identification, the Forkhead Box P2 gene (FOXP2) has maintained its singular status as the archetypal monogenic determinant implicated in Mendelian forms of human speech and language impairments. Despite the passage of two decades subsequent to its discovery, extant literature remains disproportionately sparse with regard to case-specific instances and loci of mutational perturbations. The objective of the current investigation centers on furnishing an enriched delineation of both its clinical manifestations and its mutational heterogeneity. Clinical phenotypes and peripheral blood samples were assiduously amassed from familial subjects. Whole-exome sequencing and Sanger sequencing methodologies were deployed for the unambiguous identification of potential genetic variants and for corroborating their co-segregation within the family pedigree. An exhaustive review of published literature focusing on patients manifesting speech and language disorders consequent to FOXP2 genetic anomalies was also undertaken. The investigation yielded the identification of a novel heterozygous variant, c.661del (p.L221Ffs*41), localized within the FOXP2 gene in the proband, an inheritance from his symptomatic mother. The proband presented with an array of symptoms, encompassing dysarthric speech, deficits in instruction comprehension, and communicative impediments. In comparison, the mother exhibited attenuated symptoms, including rudimentary verbalization capabilities punctuated by pronounced stuttering and dysarthria. A comprehensive analysis of articles archived in the Human Gene Mutation Database (HGMD) classified under "DM" disclosed the existence of 74 patients inclusive of the subjects under current examination, sub-divided into 19 patients with null variants, 5 patients with missense variants, and 50 patients with gross deletions or complex genomic rearrangements. A conspicuous predominance of delayed speech, impoverished current verbal abilities, verbal comprehension deficits, and learning difficulties were observed in patients harboring null or missense FOXP2 variants, as compared to their counterparts with gross deletions or complex rearrangements. Developmental delays, hypotonia, and craniofacial aberrations were exclusive to the latter cohort. The elucidated findings augment the existing corpus of knowledge on the genetic architecture influencing both the proband and his mother within this specified familial context. Of critical importance, these discoveries furnish a robust molecular framework conducive to the prenatal diagnostic evaluations of prospective progeny within this familial lineage.

The value of genome-wide analysis in craniosynostosis

Background: This study assessed the diagnostic yield of high-throughput sequencing methods in a cohort of craniosynostosis (CS) patients not presenting causal variants identified through previous targeted analysis. Methods: Whole-genome or whole-exome sequencing (WGS/WES) was performed in a cohort of 59 patients (from 57 families) assessed by retrospective phenotyping as having syndromic or nonsyndromic CS. Results: A syndromic form was identified in 51% of the unrelated cases. A genetic cause was identified in 38% of syndromic cases, with novel variants detected in FGFR2 (a rare Alu insertion), TWIST1, TCF12, KIAA0586, HDAC9, FOXP1, and NSD2. Additionally, we report two patients with rare recurrent variants in KAT6A and YY1 as well as two patients with structural genomic aberrations: one with a 22q13 duplication and one with a complex rearrangement involving chromosome 2 (2p25 duplication including SOX11 and deletion of 2q22). Moreover, we identified potentially relevant variants in 87% of the remaining families with no previously detected causal variants, including novel variants in ADAMTSL4, ASH1L, ATRX, C2CD3, CHD5, ERF, H4C5, IFT122, IFT140, KDM6B, KMT2D, LTBP1, MAP3K7, NOTCH2, NSD1, SOS1, SPRY1, POLR2A, PRRX1, RECQL4, TAB2, TAOK1, TET3, TGFBR1, TCF20, and ZBTB20. Conclusion: These results confirm WGS/WES as a powerful diagnostic tool capable of either targeted in silico or broad genomic analysis depending on phenotypic presentation (e.g., classical or unusual forms of syndromic CS).

Genetic diagnostic yield in an 11-year cohort of craniosynostosis patients

Craniosynostosis may present in isolation, 'non-syndromic', or with additional congenital anomalies/neurodevelopmental disorders, 'syndromic'. Clinical focus shifted from confirming classical syndromic cases to offering genetic testing to all craniosynostosis patients. This retrospective study assesses diagnostic yield of molecular testing by investigating prevalences of chromosomal and monogenic (likely) pathogenic variants in an 11-year cohort of 1020 craniosynostosis patients. 502 children underwent genetic testing. Pathogenic variants were identified in 174 patients (35%). Diagnostic yield was significantly higher in syndromic craniosynostosis (62%) than in non-syndromic craniosynostosis (6%). Before whole exome sequencing (WES) emerged, single-gene testing was performed using Sanger sequencing or multiplex ligation-dependent probe amplification (MLPA). Diagnostic yield was 11% and was highest for EFNB1, FGFR2, FGFR3, and IL11RA. Diagnostic yield for copy number variant analysis using microarray was 8%. From 2015 onwards, the WES craniosynostosis panel was implemented, with a yield of 10%. In unsolved, mainly syndromic, cases suspected of a genetic cause, additional WES panels (multiple congenital anomalies (MCA)/intellectual disability (ID)) or open exome analysis were performed with an 18% diagnostic yield. To conclude, microarray and the WES craniosynostosis panel are key to identifying pathogenic variants. in craniosynostosis patients. Given the advances in genetic diagnostics, we should look beyond the scope of the WES craniosynostosis panel and consider extensive genetic diagnostics (e.g. open exome sequencing, whole genome sequencing, RNA sequencing and episignature analysis) if no diagnosis is obtained through microarray and/or WES craniosynostosis panel. If parents are uncomfortable with more extensive diagnostics, MCA or ID panels may be considered.

Metopic and Sagittal Craniosynostosis in Williams Syndrome

Craniosynostosis has been previously reported in patients with Williams syndrome. Due to the associated significant cardiovascular anomalies, with an attendant increased risk of death under anaesthesia, most patients have been managed conservatively. Here we report the multidisciplinary approach in a 12-month-old female infant with Williams syndrome who has metopic and sagittal craniosynostosis. The child successfully underwent calvarial remodelling procedures, with the clinical outcome demonstrating dramatically improved global development after surgery.

The current understanding of germline predisposition in non-syndromic sagittal craniosynostosis: a systematic review

PURPOSE

The objective of this literature review was to provide a comprehensive and up-to-date overview of the current understanding of the genetic etiology for non-syndromic sagittal craniosynostosis.

METHODS

Using the PubMed database and Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), we systematically reviewed relevant records on germline genetics in children with non-syndromic sagittal craniosynostosis.

RESULTS

Two hundred two records were identified, of which 25 were included following title and abstract screening and subsequent full-text review. The 25 records in combination included 829 children with non-syndromic sagittal craniosynostosis. A likely pathogenic or pathogenic germline variant was reported for 9.8% of the 827 patients for whom germline genetic testing was performed. The reported variants were distributed across 50 different genes, with more than one variant detected in 13 genes.

CONCLUSION

Based on the existing literature, genetic predisposition is likely to play a role in at least 9% of children with non-syndromic sagittal craniosynostosis. Future studies will benefit from international consensus in terms of diagnostic nomenclature and a higher level of standardization across study methodologies and bioinformatic approaches.

Review of Recurrently Mutated Genes in Craniosynostosis Supports Expansion of Diagnostic Gene Panels

Craniosynostosis, the premature fusion of the cranial sutures, affects ~1 in 2000 children. Although many patients with a genetically determined cause harbor a variant in one of just seven genes or have a chromosomal abnormality, over 60 genes are known to be recurrently mutated, thus comprising a long tail of rarer diagnoses. Genome sequencing for the diagnosis of rare diseases is increasingly used in clinical settings, but analysis of the data is labor intensive and involves a trade-off between achieving high sensitivity or high precision. PanelApp, a crowd-sourced disease-focused set of gene panels, was designed to enable prioritization of variants in known disease genes for a given pathology, allowing enhanced identification of true-positives. For heterogeneous disorders like craniosynostosis, these panels must be regularly updated to ensure that diagnoses are not being missed. We provide a systematic review of genetic literature on craniosynostosis over the last 5 years, including additional results from resequencing a 42-gene panel in 617 affected individuals. We identify 16 genes (representing a 25% uplift) that should be added to the list of bona fide craniosynostosis disease genes and discuss the insights that these new genes provide into pathophysiological mechanisms of craniosynostosis.