Molecular cloning of the human Hand1 gene/cDNA and its tissue-restricted expression in cytotrophoblastic cells and heart

The basic helix-loop-helix (bHLH) factor Hand1 plays a role in the developi ng chicken heart and is required for trophoblast giant cell differentiation and cardiac looping of mouse embryonic development. Here, we report the cl oning of the human Hand1 cDNA and gene from a heart-specific cDNA library a nd a genomic lambda-DNA library, respectively, We present the nucleotide se quence of a 1.75 kb cDNA clone, encoding the presumptive 215 amino acid hum an Hand1 protein, and show homology comparison of the conserved bHLH region between different species. In vitro transcription-translation of Hand1 mRN A and analysis of protein size suggest that the Hand1 polypeptide is (post) translationally modified. By Southern blot analysis we demonstrate that the isolated genomic DNA clone harbours the entire Hand1 gene and describe mol ecular structure and sequences of the two 799 and 938 bp exons and the sing le 1.56 kb intron. The expression pattern of the mRNA in different human ti ssues revealed that Hand1 transcripts are restricted to the heart, suggesti ng that the protein could be required for cardiac-specific gene transcripti on and function in adults. Hand1 transcripts were undetectable in a non-tum origenic villous trophoblast cell line, immunopurified cytotrophoblasts und ergoing in vitro differentiation, and first trimester placental tissue, sug gesting that the transcription factor is not involved in the development of villous and extravillous trophoblast cell lineages. Hand1 mRNA, however, w as abundantly expressed in cytotrophoblastic Jeg-3 and BeWo cells, suggesti ng that Hand1 could be required for early trophoblast differentiation. (C) 1998 Elsevier Science B.V. All rights reserved.