Matrix metalloproteinase-9 maps to the distal end of chromosome 2 in the mouse

The activity and expression of matrix metalloproteinase-9/gelatinase B(MMP-9), an enzyme implicated in the implantation process in mice, was investigated in normal and parthenogenetic blastocyst outgrowths. Conditioned media from parthenogenetic blastocysts after 4 days of culture had reduced levels of MMP-9 activity compared to conditioned medium from normal outgrowths, levels of MMP-9 mRNA assayed by reverse transcription-polymerase chain reaction methods were also reduced in parthenogenetic blastocysts compared io normal outgrowths. Geneiic mapping studies showed that Mmp9 maps to the distal end of chromosome 2 near the proxima boundary of a region affected by genomic imprinting. Both parental alleles of Mmp9, however, are expressed in 11.5-day embryos derived from interspecific crosses of Mus musculus and Mus spretus. Thus, loss of MMP-9 activity in parthenogenetic blastocysts does not appear to be due to imprinting but, rather, due io a defect of trophoblast giant cell proliferation and differentiation. (C) 1997 Wiley-iiss, Inc.