Isolation and characterization of mammary cDNA differentially expressed inlethal milk mutation mice

Lethal milk (lm) mutation in C57BL/6J inbred mice results in the reduction of zinc content in the milk and causes fatal neonatal zinc deficiency. Zinc injection to lm pups after birth help, them to overcome severe neonatal zi nc deficiency and to maintain the normal body growth of lm pups. Thus, lm m utation displays a specific effect on the zinc content of the milk during l actation. The decrease in zinc content of them milk is not due to the low b ody zinc status in lactating lm dams. Also, oral zinc supplementation in la ctating lm dams does not correct the low concentration of zinc in the milk. These findings suggest that lm mutation results in the defective cellular transport of zinc. The defective zinc transport might alter the expression of mammary genes because cellular zinc plays a critical role in diverse cel lular functions. To investigate the effect of lm mutation on the expression of mammary genes, the differentially expressed cDNAs in lm mammary gland ( MG) were explored using the mRNA differential display (DD) gel. One of the isolated cDNAs (M3) was expressed in the lm MG two times greater than that in the normal MG. The cloned partial M3 cDNA was shown to have the similari ties to the unknown functional cDNAs in the yeast and human tissues. The M3 cDNA might have a common function in both lower and higher eukaryotes. The M3 mRNA is rich in the brain and the MG, but not in the liver and kidney. Hence, the M3 cDNA may have a certain function associated with the brain an d the MG. More information regarding the cloned M3 cDNA might be provided b y screening of the full length of M3 cDNA from cDNA library. J. Trace Elem. Exp. Med. 14:371-382, 2001. (C) 2001 Wiley-Liss. Inc.