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Updated: Jul 17, 2026
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Simultaneous Mapping and Quantitation of Ribonucleotides in Human Mitochondrial DNA
Published on: November 14, 2017
Hydroxymethylbilane synthase: complete genomic sequence and amplifiable polymorphisms in the human gene
H W Yoo1, C A Warner, C H Chen
1Division of Medical and Molecular Genetics, Mount Sinai School of Medicine, New York, New York 10029.
Genomics
|January 1, 1993
Summary
Diagnosing acute intermittent porphyria (AIP) is challenging. Researchers sequenced the HMB-synthase gene, identifying mutations and improving diagnostic PCR methods for this rare genetic disorder.
Area of Science:
- Genetics
- Biochemistry
- Molecular Biology
Background:
- Acute intermittent porphyria (AIP) is an autosomal dominant disorder of heme biosynthesis.
- It stems from reduced hydroxymethylbilane synthase (HMB-synthase) activity, leading to severe neurological attacks in affected individuals.
- Current biochemical diagnostic methods for heterozygous carriers are problematic.
Purpose of the Study:
- To isolate and sequence the complete human HMB-synthase gene, including its 5' flanking region.
- To identify mutations and Restriction Fragment Length Polymorphisms (RFLPs) for improved AIP diagnosis.
- To develop enhanced Polymerase Chain Reaction (PCR)-based detection methods for diagnostic RFLPs.
Main Methods:
- Isolation and complete sequencing of the human HMB-synthase gene (10,024 bp) and its 5' flanking region (1.1 kb).
- Analysis of gene structure, including exon-intron boundaries and repetitive elements.
- Identification and characterization of regulatory elements in the promoter regions.
- Mapping and sequencing of known RFLPs within intron 1.
- Development of improved PCR-based detection assays for identified RFLPs.
Main Results:
- The HMB-synthase gene comprises 15 exons and 14 introns, with all intron/exon boundaries conforming to the GT/AG consensus rule.
- The 5' flanking region contains putative regulatory elements for a housekeeping promoter.
- Intron 1 harbors an erythroid-specific promoter with various regulatory motifs.
- Specific nucleotide variants and locations for four known RFLPs (MspI, PstI, ApaLI, BstNI) in intron 1 were precisely identified.
- Optimized PCR methods were established for detecting these RFLPs.
Conclusions:
- The complete sequence of the HMB-synthase gene provides a foundation for further genetic studies of AIP.
- The identified RFLPs and developed PCR methods offer improved tools for the biochemical diagnosis of heterozygous AIP carriers.
- These advancements facilitate the identification of mutations and enhance diagnostic capabilities for this rare genetic disorder.
