Canine mammary growth hormone gene transcription initiates at the pituitary-specific start site in the absence of Pit-1.
Growth hormone (GH) gene expression has been reported in the mammary glands of various mammalian species. The mechanism by which the GH gene becomes activated in extrapituitary tissues is currently unclear. We have characterized the canine mammary and pituitary GH gene transcripts by Northern blot, 5'- and 3'-RACE (rapid amplification of cDNA ends), and DNA sequence analysis. Northern blot analysis detected GH gene transcripts in mammary glands of dogs which were exposed to high levels of progestins. The mammary and pituitary GH cDNAs were shown to be identical in both the coding region and untranslated regions. Pituitary GH gene expression is highly dependent upon the transcription factor Pit-1. Analysis of Pit-1 gene expression using RT-PCR followed by Southern hybridization revealed a strong pituitary signal but faint, weak or no hybridization signals in mammary gland samples. Among the negative samples were progestin-treated dogs with high mammary GH gene expression. These findings indicate that mammary and pituitary GH gene transcripts originate from the same transcription start site but are regulated differentially.
Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, University of Utrecht, The Netherlands.
I S
IS
Lantinga-van Leeuwen
M
M
Oudshoorn
J A
JA
Mol
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000502:physiology*; D004285:Dogs; D005260:Female; D005786:Gene Expression Regulation / Q000502:physiology*; D013006:Growth Hormone / Q000502:physiology*; D008321:Mammary Glands, Animal / Q000502:physiology*; D008969:Molecular Sequence Data; D010902:Pituitary Gland / Q000502:physiology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D050817:Transcription Factor Pit-1; D014157:Transcription Factors / Q000502:physiology*; D014158:Transcription, Genetic
D004268:DNA-Binding Proteins; D012333:RNA, Messenger; D050817:Transcription Factor Pit-1; D014157:Transcription Factors; D013006:Growth Hormone