Related Experiment Videos
Three RFLPs defining a haplotype associated with the common mutation in human medium-chain acyl-CoA dehydrogenase
1Department of Pediatrics, Washington University School of Medicine, St Louis, MO.
Abstract:
Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is a common inborn error of fatty-acid oxidation and may cause sudden infant death. Previous studies revealed that (i) homozygosity for an A-to-G mutation at nucleotide 985 of the mRNA coding region (A985G) is an extremely common cause of MCAD deficiency and (ii) MCAD deficiency is strongly associated with a particular haplotype for RFLPs for BanII, PstI, and TaqI. TaqI allele 2 is always associated with the A985G mutation in human MCAD deficiency. In this study, we have delineated the molecular basis of the RFLPs for PstI, BamHI, and TaqI in the human MCAD gene. Our results prove that the three RFLPs are caused by point mutations in the 8 kb of DNA encompassing exons 8-10 of the human MCAD gene. The TaqI polymorphism is caused by a C-to-A substitution 392 bp upstream of the exon 8, and the PstI and BamHI polymorphisms are due to T-to-C and G-to-A substitutions, respectively, which are 727 and 931 bp downstream of exon 10 respectively. All three RFLPs lie within Alu repetitive sequences. Comparison of intronic sequences immediately following exon 10 from two normal individuals with different haplotypes showed that this region contains densely packed Alu repeats and is highly polymorphic. Our results are consistent both with a founder effect as the cause of the high prevalence of a single (A985G) mutation in MCAD deficiency and with its association with a particular haplotype for these intragenic RFLPs.
Insights
Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency, a common fatty-acid oxidation disorder, is linked to a specific mutation (A985G). This study identifies the molecular basis of associated RFLPs, clarifying the genetic underpinnings of MCAD deficiency.
Area of Science:
- Biochemistry
- Genetics
- Molecular Biology
Background:
- Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is a prevalent inherited metabolic disorder affecting fatty-acid oxidation.
- This condition is frequently linked to the A985G mutation and specific restriction fragment length polymorphisms (RFLPs).
Purpose of the Study:
- To elucidate the molecular basis of PstI, BamHI, and TaqI RFLPs within the human MCAD gene.
- To understand the genetic association between MCAD deficiency, the A985G mutation, and specific haplotypes.
Main Methods:
- Analysis of DNA sequences encompassing exons 8-10 of the human MCAD gene.
- Identification of point mutations responsible for TaqI, PstI, and BamHI polymorphisms.
- Comparison of intronic sequences in individuals with different haplotypes.
Main Results:
- The TaqI, PstI, and BamHI RFLPs are caused by specific point mutations within or downstream of exons 8-10.
- These polymorphisms are located within Alu repetitive sequences.
- The study confirms the association between the A985G mutation and a particular RFLP haplotype.
Conclusions:
- The identified point mutations explain the observed RFLPs in the MCAD gene.
- Results support a founder effect contributing to the high prevalence of the A985G mutation.
- The findings clarify the genetic architecture underlying MCAD deficiency and its associated haplotype.