Barth syndrome: TAZ gene mutations, mRNAs, and evolution

Area of Science:

• Genetics
• Molecular Biology
• Biochemistry

Background:

• Barth syndrome is an X-linked disorder characterized by dilated cardiomyopathy, neutropenia, and failure to thrive.
• The TAZ gene, implicated in Barth syndrome, exhibits complex alternative splicing.
• Previous research suggested multiple transcription initiation sites and functional significance of various splice variants, including those involving exon 5.

Purpose of the Study:

• To investigate the TAZ gene's alternative splicing patterns in Barth syndrome.
• To determine the functional significance of different TAZ mRNA splice variants, particularly those involving exon 5.
• To clarify the TAZ gene's transcriptional and translational regulation.

Main Methods:

• Reverse transcription polymerase chain reaction (RT-PCR) was used to analyze TAZ mRNA from cultured lymphocytes of Barth syndrome patients and healthy controls.
• Comparative analysis included TAZ genes and mRNAs from primate species.
• Bioinformatic and evolutionary analyses were performed to understand exon evolution.

Main Results:

• A single transcription initiation site was identified for the TAZ gene.
• The normal alternatively spliced TAZ mRNA variants are limited to full-length, delta5, delta7, and delta5delta7.
• Two functional protein variants, delta5 and full-length, were identified in lymphocytes, with exon 5 gaining conserved spliced status in hominoid primates.

Conclusions:

• The TAZ gene exhibits a defined set of alternatively spliced variants, contrary to previous assumptions of extensive heterogeneity.
• Only two TAZ protein variants (delta5 and full-length) appear to be functional in lymphocytes.
• The evolution of exon 5 in primates suggests its importance in TAZ function, potentially explaining its role in Barth syndrome pathogenesis.