P.A. Akkari

Assignment of the human a-tropomyosin gene TPM3 to 1q22-q23 by fluorescence in situ hybridisation

The human tropomyosin 3 (TPM3) gene was previously localized to chromosome 1. The non-muscle isoform of the TPM3 gene product becomes fused to a gene product from the tyrosine kinase receptor gene (NTRK1), previously localized to 1q23-->q24, to generate an active oncogene. Two sequence tagged sites spanning three exons and two introns in the carboxy coding region of the gene were used to localize TPM3 to 1q22-->q23 by fluorescence in situ hybridization. This localization now places the NTRK1 and TPM3 genes in close proximity, so that a gene fusion rearrangement would not be cytologically detected. The 1q22-->q23 localization of TPM3 is within the NEM1 locus associated with autosomal dominant nemaline myopathy, making TPM3 a candidate for this disorder.

Assignment of the human skeletal muscle a-tropomyosin gene (TPM1) to band 15q22 by fluorescence in situ hybridization

A sequence-tagged site (STS) was developed for the human skeletal muscle alpha-tropomyosin gene (TPM1) and used to isolate a genomic clone, lambda TPM1.1, containing part of the TPM1 gene. Fluorescence in situ hybridization of this clone to metaphase chromosome spreads localised TPM1 to chromosome band 15q22. This localisation in humans is consistent with that recently described for the mouse.

Assignment of the human beta tropomyosin gene (TPM2) to band 9p13 by fluorescence in situ hybridisation

A sequence tagged site (STS) was developed for the human beta tropomyosin gene (TPM2). The STS was used to amplify DNA from somatic cell hybrids to localise TPM2 to human chromosome 9. Genomic clones isolated with the STS product were in turn used in fluorescence in situ hybridisation to metaphase chromosome spreads to further localise TPM2 to 9p13.

Assignment of the human slow skeletal muscle troponin gene (TNNI1) to 1q32 by fluorescence in situ hybridisation

The human gene for slow-twitch skeletal muscle troponin I (TNNI1) has previously been mapped to 1q12-->qter using somatic cell hybrids. The TNNI1 locus has now been further localised to 1q32 using fluorescence in situ hybridization. This result confirms the previous assignment of this locus and maps the gene to a single chromosome band.