Human ferrochelatase: a novel mutation in patients with erythropoietic protoporphyria and an isoform caused by alternative splicing

ObjectiveMutations in HESX1 represent a rare cause of GH deficiency (GHD) associated with a broad spectrum of other anomalies. We searched for causative mutations in a cohort of 244 Italian patients affected by combined and isolated GHD (IGHD).MethodsThe HESX1 gene-coding region and exon–intron boundaries were screened by denaturing HPLC scanning.ResultsA novel mutation adjacent to the invariant donor splice site of intron 2 (c.357+3G>A) was identified at the heterozygous state in an IGHD patient. The in vitro and in vivo mRNA analysis of the wild-type HESX1 allele revealed the presence of the whole cDNA and two isoforms lacking exon 2 and exons 2–3 respectively. The mutant HESX1 allele yielded only two splicing products, the whole cDNA and the cDNA missing exons 2–3, whereas the mRNA lacking exon 2 was absent. An in vitro assay demonstrated that the exon 2-deleted mRNA, predicting a prematurely truncated protein, is subjected to nonsense-mediated mRNA decay (NMD).ConclusionsThe c.357+3G>A mutation prevents the generation of one of the alternative isoforms normally produced by the wild-type allele, predicting a truncated HESX1 protein. The mutation is likely to cause IGHD in the heterozygous patient by interfering with the downregulation of HESX1 expression mediated by alternative splicing and NMD.Our results open new insight into the mechanism of HESX1 regulation suggesting that the coupling of alternative splicing and NMD might play a fundamental role in directing the HESX1 expression, and that the alteration of this process might lead to severe consequences.

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A novel mutation in erythropoietic protoporphyria: an aberrant ferrochelatase mRNA caused by exon skipping during RNA splicing

Biochimica et Biophysica Acta (BBA) - Molecular Basis of Disease ◽

10.1016/0925-4439(93)90112-e ◽

1993 ◽

Vol 1181 (2) ◽

pp. 198-200 ◽

Cited By ~ 23

Author(s):

Xiuhua Wang ◽

Maureen Poh-Fitzpatrick ◽

Damaris Carriero ◽

Ludmila Ostasiewicz ◽

Timothy Chen ◽

...

Keyword(s):

Rna Splicing ◽

Novel Mutation ◽

Exon Skipping ◽

Erythropoietic Protoporphyria

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Linking transcription, RNA polymerase II elongation and alternative splicing

Biochemical Journal ◽

10.1042/bcj20200475 ◽

2020 ◽

Vol 477 (16) ◽

pp. 3091-3104 ◽

Cited By ~ 1

Author(s):

Luciana E. Giono ◽

Alberto R. Kornblihtt

Keyword(s):

Gene Expression ◽

Alternative Splicing ◽

Rna Polymerase Ii ◽

Environmental Changes ◽

Transcription Elongation ◽

Single Gene ◽

Regulation Of Gene Expression ◽

Regulation Of Transcription ◽

Stepping Stones ◽

Eukaryotic Transcription

Gene expression is an intricately regulated process that is at the basis of cell differentiation, the maintenance of cell identity and the cellular responses to environmental changes. Alternative splicing, the process by which multiple functionally distinct transcripts are generated from a single gene, is one of the main mechanisms that contribute to expand the coding capacity of genomes and help explain the level of complexity achieved by higher organisms. Eukaryotic transcription is subject to multiple layers of regulation both intrinsic — such as promoter structure — and dynamic, allowing the cell to respond to internal and external signals. Similarly, alternative splicing choices are affected by all of these aspects, mainly through the regulation of transcription elongation, making it a regulatory knob on a par with the regulation of gene expression levels. This review aims to recapitulate some of the history and stepping-stones that led to the paradigms held today about transcription and splicing regulation, with major focus on transcription elongation and its effect on alternative splicing.

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