Author(s): Liu JP, Baker J, Perkins AS, Robertson EJ, Efstratiadis A
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Abstract Newborn mice homozygous for a targeted disruption of insulin-like growth factor gene (Igf-1) exhibit a growth deficiency similar in severity to that previously observed in viable Igf-2 null mutants (60\% of normal birthweight). Depending on genetic background, some of the Igf-1(-/-) dwarfs die shortly after birth, while others survive and reach adulthood. In contrast, null mutants for the Igf1r gene die invariably at birth of respiratory failure and exhibit a more severe growth deficiency (45\% normal size). In addition to generalized organ hypoplasia in Igf1r(-/-) embryos, including the muscles, and developmental delays in ossification, deviations from normalcy were observed in the central nervous system and epidermis. Igf-1(-/-)/Igf1r(-/-) double mutants did not differ in phenotype from Igf1r(-/-) single mutants, while in Igf-2(-)/Igf1r(-/-) and Igf-1(-/-)/Igf-2(-) double mutants, which are phenotypically identical, the dwarfism was further exacerbated (30\% normal size). The roles of the IGFs in mouse embryonic development, as revealed from the phenotypic differences between these mutants, are discussed.
This article was published in Cell
and referenced in Journal of Diabetes & Metabolism