New member of the Snf1/AMPK kinase family, Melk, is expressed in the mouse egg and preimplantation embryo

Abstract

The initial phase of mammalian preimplantation development is directed by stored maternal mRNAs and their encoded proteins, yet most of the molecules controlling this process have not been described. We have used differential display analysis of cDNA libraries prepared from unfertilized eggs and preimplantation embryos to isolate three maternal cDNAs that represent novel genes exhibiting different patterns of expression during this developmental period. One of these, Melk, encodes a protein with a kinase catalytic domain and a leucine zipper motif, a new member of the Snf1/AMPK family of kinases. This gene product may play a role in the signal transduction events in the egg and early embryo.

Expression of Melk, a new protein kinase, during early mouse development

“…Melk transcripts are easily detectable in ovulated mouse eggs and barely detectable in 2-cell stage embryos; in later developmental stages they are increasingly detectable. A similar expression pattern has been described for other maternal genes (Heyer et al, 1997;Bachvarova, 1989;Ohsugi et al, 1996;Oh et al, 1997). The absence of Melk mRNA in 2-cell stage embryos is probably due to the active degradation of maternal transcripts during this stage (Clegg and Piko, 1983;Paynton et al, 1988).…”

“…Besides the previously reported Melk transcript (Heyer et al, 1997), we have identified a second, shorter transcript, Melk2. The Melk2 transcripts, which are coexpressed with Melk transcripts in the ovary and during embryogenesis, lack 56 amino acids in the distal region of the kinase domain, i.e., half of the subdomain X and subdomains XI and XII.…”

Expression ofMelk, a new protein kinase, during early mouse development

“…Melk transcripts were easily detected using RT‐PCR in ovulated eggs, barely detectable in 2‐cell stage embryos and were again present in 8‐cell stage embryos and blastocysts (Heyer et al, 1997). Whole‐mount in situ hybridization with a Melk ‐specific antisense probe allowed further determination of the spatial localization of the transcripts (Fig.…”

The changing AMPK expression profile in differentiating mouse skeletal muscle myoblast cells helps confer increasing resistance to apoptosis

“…However, we only detected the p50 and not the p72 isoform of MELK, which may reflect an alternative MELK translation product as suggested by Gil et al (1997). That MELK is only expressed in the undifferentiated, proliferating C2C12 myoblasts could imply that it has a role in promoting proliferation while inhibiting differentiation programmes, as in other cells (Heyer et al 1997;Gil et al 1998;Davezac et al 2002;Nakano et al 2005). For example, MELK plays an important role in preimplantation embryonic development (Suzuki et al 2003b).…”