International Mammalian Genome Society

logo18th International Mouse Genome Conference

17-22 October 2004, Seattle, USA


Kirn-Safran CB, Focht RJ, Mari ER, Carson DD

University of Delaware Department of Biological Sciences, Newark, United States

HIP is a heparin/heparan sulfate interacting protein identical to ribosomal protein L29 that is not believed to be essential for translation, but rather plays a role in translation efficiency.  There is increasing evidence that targeted gene disruption of specific ribosomal protein genes is lethal in embryos prior to implantation.  Because high levels of HIP/RPL29 are found in embryonic stem (ES) cells and in all types of proliferating and developing tissues, we hypothesize that the presence of HIP/RPL29 is essential for normal early embryonic growth.  In particular, we believe that a strict regulation of HIP/RPL29 expression is required to maintain proliferation and avoid commitment of stem cell progenitors to specific cellular differentiation programs.

To investigate the role of HIP/RPL29 expression during early development, we targeted one of the two alleles of Hip/RPl29 gene in a pluripotent mouse ES cell line of the 129S7 background.  Mutant ES cell contribution was assessed in vivo by breeding chimeras obtained after microinjection of Hip/Rpl29 +/- ES cells into C57BL/6N host blastocysts.  Our results show that Hip/Rpl29 +/- ES cells display a dramatically reduced germ cell potential. Thus, a significant number of chimeric males highly derived from the ES cell line, as determined by the strong contribution of the dominant Agouti gene to their coat color, primarily transmitted C57Bl/6N sperm to their progeny.  This result suggests that a mutation in the Hip/Rpl29 gene is detrimental to the maintenance of the ES cell undifferentiated phenotype, and is consistent with our previous studies that demonstrated that a knock-down of HIP/RPL29 mRNA is associated with an accelerated differentiation potential of a multipotent stem cell line into cartilage-like cells.  Additional studies are currently focusing on determining whether Hip/Rpl29 -/- null embryos and ES lines are viable.  In conclusion, our data indicate that HIP/RPL29 constitutes a candidate regulator of stem cell differentiation. (Supported by Lalor grant to C.B.K.S and NIH grant HD25235 to D.D.C.)

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