A lethal deletion on mouse chromosome 7 affects regulation of liver-cell-specific functions: posttranscriptional control of serum protein and transcriptional control of aldolase B synthesis.

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Abstract
Steady-state levels of mRNA were determined for the serum proteins albumin, .alpha.-fetoprotein (AFP) and transferrin, as well as for aldolase B in livers of newborn mice homozygous for a radiation-induced lethal deletion (c14CoS) in chromosome 7. Deficiencies in synthesis and secretion of the serum proteins as well as in activities of certain liver-specific enzymes characterize these homozygotes. The results of RNA dot and gel-blot hybridizations with the respective cloned c[complementary]DNA probes showed a decrease to one-fourth of aldolase B mRNA levels in homozygous mutant livers compared to normal littermates, in contrast to normal levels of mRNA sequences for the 3 serum proteins in the mutants. The mRNA sequences were present as mature mRNA molecules in both mutant and normal littermate livers. The deficiencies of liver-specific serum proteins and those of the enzymes caused by the lethal deletions around the albino locus on chromosome 7 of the mouse are due to different causes. In the case of the liver-specific enzyme examined, i.e., aldolase B, control at the level of transcription or of message stability is affected in the homozygous deletion mutants, whereas the deficiencies of serum proteins are not reflected on the mRNA level and owe their origin to an effect on a posttranscriptional or translational level. The deleted portion of the genome includes genes concerned with the control and regulation of liver cell differentiation.