The mouse relaxin gene: nucleotide sequence and expression

Abstract

Relaxin is a polypeptide hormone that has a variety of physiological effects both on remodelling of collagen and on uterine contractility. These are most apparent during pregnancy. The sequences of relaxin cDNAs derived from ovaries of late-pregnant random-bred Swiss mice have been established. Multiple subclones obtained from three independent polymerase chain reaction experiments were found to encode relaxins which were identical except at position 11 in the A chain (Ile or Val). All mouse relaxin cDNAs expressed in the ovary during pregnancy had an extra tyrosine inserted prior to the final A chain cysteine residue, a result confirmed by direct sequencing of relaxin peptides. Whilst this tyrosine insertion must have local effects on the folding of the A chain, structure-activity studies will clarify whether it perturbs functional interaction with the relaxin receptor. We have shown that there is a single relaxin gene in the mouse genome, and that expression during pregnancy occurs in the ovary but is not detectable in the placenta, uterus or fetus.

Human Relaxin Gene 3 (H3) and the Equivalent Mouse Relaxin (M3) Gene

“…The obtained transcript size was consistent with the predicted size based on the M3 relaxin transcript sequence (ϳ1 kb) plus a poly(A) tail (ϳ200-bp). In contrast, no M1 expression was seen in brain poly(A) RNA although a strong signal was seen in the ovarian total RNA of the same size as that seen in the total RNA blot and consistent with the size (ϳ1 kb) published previously (30).…”

“…Although PCR data suggest that the M3 relaxin gene is expressed in the ovary, it seems unlikely that it is a luteal cell product like H2 (3) and M1 relaxin (30). Northern blot analyses and preliminary in situ hybridization histochemistry data of ovaries from late pregnant mice failed to detect any specific expression, and PCR studies using human CL of early pregnancy failed to amplify a specific transcript.…”

“…Furthermore, the A-chain of M3 relaxin is more typical in structure to other members of the relaxin peptide family, wherein the terminal A-chain cysteine residue is separated from the intra-disulfide bond-linked cysteine by eight amino acids. The previously characterized M1 relaxin peptide stands out from all the known relaxin sequences by having nine residues in this sequence region (30). It remains to be seen if the relaxin bioactivity of M3 is greater than that of M1 relaxin.…”

“…A polyadenylation signal is present in the 3Ј-untranslated region of both genes, in a position 582 and 448 bp downstream from an in-frame TAG stop codon for the human and mouse genes, respectively. A single intron interrupts the coding region in an identical position in the sequence of both genes, corresponding to a similar position to that of other relaxin and insulin family members (2,30,33). The H3 relaxin gene is localized on chromosome 19 at 19p13.3, whereas the mouse gene is located on chromosome 8 at 8C2.…”

“…The human sequence has been designated H3 relaxin, for human gene 3, as it is the third relaxin gene to be discovered in the human. We have designated the mouse sequence as M3 relaxin for consistency, although there is currently only one other relaxin gene identified in the mouse (30).…”