Until cytoplasmic recapping was discovered, decapping was thought to irreversibly destine an mRNA to degradation. Contradicting this idea, we readily observe mRNAs targeted by cytoplasmic capping in uncapped, yet stable forms. 5′ rapid amplification of cDNA ends (RACE) shows that nearly all uncapped ends correspond to capped analysis of gene expression tags and that the recapping of ZNF207 mRNA may be restricted to a single splice isoform. Here, a modified RACE approach detected uncapped 5′ RNA ends mapping to 46 mRNAs in cells expressing a dominant negative cytoplasmic capping enzyme and in normal cells. Eleven of 46 cloned mRNAs also contained splice isoform‐limiting sequences. Collectively, these data reinforce earlier work and suggest that alternative splicing may play a role in targeting transcripts for – and/or determining the position of – cytoplasmic capping.

Nonsyndromic cleft lip with or without cleft palate (NSCL/P) is a common, severe craniofacial malformation that imposes significant medical, psychosocial, and financial burdens. NSCL/P is a multifactorial disorder with genetic and environmental factors playing etiologic roles. Currently, only 25% of the genetic variation underlying NSCL/P has been identified by linkage, candidate gene, and genome-wide association studies. In this study, whole genome sequencing (WGS) and genome-wide genotyping followed by polygenic risk score (PRS) and linkage analyses were used to identify the genetic etiology of NSCL/P in a large three-generation family. We identified a rare missense variant in PDGFRA (c.C2740T; p.R914W) as potentially etiologic in a gene-based association test using pVAAST (P = 1.78 x 10−4) and showed decreased penetrance. PRS analysis suggested that variant penetrance was likely modified by common NSCL/P risk variants, with lower scores found among unaffected carriers. Linkage analysis provided additional support for PRS-modified penetrance, with a 7.4-fold increase in likelihood after conditioning on PRS. Functional characterization experiments showed that the putatively causal variant was null for signaling activity in vitro; further, perturbation of pdgfra in zebrafish embryos resulted in unilateral orofacial clefting. Our findings show that a rare PDGFRA variant, modified by additional common NSCL/P risk variants, have a profound effect on NSCL/P risk. These data provide compelling evidence for multifactorial inheritance long postulated to underlie NSCL/P and may explain some unusual familial patterns.

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Until cytoplasmic recapping was discovered, decapping was thought to irreversibly destine an mRNA to degradation. Contradicting this idea, we readily observe mRNAs targeted by cytoplasmic capping in uncapped, yet stable forms. 5' RACE shows that nearly all uncapped ends correspond to CAGE tags and that the recapping of ZNF207 mRNA may be restricted to a single splice isoform. A modified RACE approach detected uncapped 5' RNA ends mapping to 46 mRNAs in dominant negative cytoplasmic capping enzyme expressing and normal cells. 11 of 46 cloned mRNAs also contained splice isoform-limiting sequences. Collectively, these data reinforce earlier work and suggest that alternative splicing may play a role in targeting transcripts forand/or determining the position of-cytoplasmic capping.