Zebrafish mutants calamity and catastrophe define critical pathways of gene-nutrient interactions in developmental copper metabolism.

Nutrient availability is an important environmental variable during development that has significant effects on the metabolism, health, and viability of an organism. To understand these interactions for the nutrient copper, we used a chemical genetic screen for zebrafish mutants sensitive to developmental copper deficiency. In this screen, we isolated two mutants that define subtleties of copper metabolism. The first contains a viable hypomorphic allele of atp7a and results in a loss of pigmentation when exposed to mild nutritional copper deficiency. This mutant displays incompletely penetrant skeletal defects affected by developmental copper availability. The second carries an inactivating mutation in the vacuolar ATPase that causes punctate melanocytes and embryonic lethality. This mutant, catastrophe, is sensitive to copper deprivation revealing overlap between ion metabolic pathways. Together, the two mutants illustrate the utility of chemical genetic screens in zebrafish to elucidate the interaction of nutrient availability and genetic polymorphisms in cellular metabolism.

Mutations in the murine homologue of the Menkes gene in dappled and blotchy mice.

The murine homologue of the Menkes disease gene (MNK) was isolated from cDNA libraries, using human cDNA clones as probes, and by PCR. The predicted amino acid sequence shows a high level of identity (89.9%) with the human protein, and the predicted functional domains in the human protein are present. Using probes to the mouse Mnk gene, we found that the mottled dappled mutation was caused by alteration in the Mnk locus and lack of expression of Mnk RNA. Tissues of the blotchy mouse contained two larger sizes of MNK mRNA demonstrating a likely defect in RNA splicing. Thus, the mottled locus is homologous to the human MNK locus and dappled and blotchy are allelic mutations in this gene.

Effects of oral copper administration to pregnant heterozygous brindled mice on fetal viability and copper levels.

Copper (6 ppm) was administered to pregnant heterozygous brindled and normal mice from 13 to 18 days gestation. The copper and zinc concentrations in the cerebrum, cerebellum, liver, and kidneys of mothers and their fetuses were determined. The placental concentrations in fetuses of heterozygous mothers administered copper were also determined. The heterozygous mothers had smaller numbers of live fetuses than the normal mothers, but had the same number as normal mothers when copper was administered. The hepatic copper concentration in the heterozygous mothers was lower than that in the normal mothers and was not increased by the administration. The body and tissue wet weights of all fetuses were unaffected by the maternal genotype or drinking fluid. The cerebral copper concentrations in hemizygous and heterozygous fetuses were increased by the copper administration but did not reach normal levels. The hepatic and renal concentrations remained unchanged. The cerebral copper concentrations in normal fetuses of both heterozygous and normal mothers were increased by the copper administration. The copper administration increased the copper concentrations in liver of normal fetuses of heterozygous mothers and in kidneys of normal fetuses of normal mothers. The placental copper concentration in hemizygous fetuses was higher than those in heterozygous and normal fetuses. These results suggested that oral copper administration to pregnant females could improve an abnormal copper distribution in hemizygous and heterozygous fetuses without affecting fetal growth.

Cerebral malformation associated with metabolic disorder. A report of 2 cases.

A clinical and neuropathological study is presented of two cases each of which showed neuronal heterotopia. Microgyria was also present in one case. One patient was suffering from a degenerative disorder affecting the white matter. The other was a case of Menkes' disease. It is suggested that the antenatal damage may have been caused by an imbalance of the maternal metabolism, the predisposing factor being the mother's carrier state for a metabolic defect. This is the first report of teratogenesis in a case of Menkes' disease. It is also noted that in this case there is interference with the postnatal as well as the antenatal development of the brain.