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. Con ditioned media from parthenogenetic blastocysts after 4 days of cultur e had reduced levels of MMP-9 activity compared to conditioned medium from normal outgrowths, levels of MMP-9 mRNA assayed by reverse transc ription-polymerase chain reaction methods were also reduced in parthen ogenetic blastocysts compared io normal outgrowths. Geneiic mapping st udies showed that Mmp9 maps to the distal end of chromosome 2 near the proxima boundary of a region affected by genomic imprinting. Both par ental alleles of Mmp9, however, are expressed in 11.5-day embryos deri ved 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 gi ant cell proliferation and differentiation. (C) 1997 Wiley-iiss, Inc.