Leber's hereditary optic neuropathy is a maternally inherited disease resulting in optic nerve degeneration and cardiac dysrhythmia. A mitochondrial DNA replacement mutation was identified that correlated with this disease in multiple families. This mutation converted a highly conserved arginine to a histidine at codon 340 in the NADH dehydrogenase subunit 4 gene and eliminated an Sfa NI site, thus providing a simple diagnostic test. This finding demonstrated that a nucleotide change in a mitochondrial DNA energy production gene can result in a neurological disease.

Mutations in presenilin 1 (PS1) are linked to early onset of familial Alzheimer's disease (FAD) and are shown to foster production of Abeta1-42/43 in FAD patients and transgenic mice. PS1 null mice are embryonic lethal and exhibit axial skeleton malformation and CNS defects. We show that transgenic mouse lines expressing either the wild-type human PS1 protein or human PS1 with the A246E FAD mutation can rescue the PS1 knockout mouse from embryonic lethality to similar degrees, indicating that the mutation does not lead to loss of PS1 function during development. Furthermore, a 50% reduction of PS1 activity in PS1(+/-) mice does not lead to Abeta1-42/43 increase, whereas expression of human mutant PS1 on murine PS1 null background is sufficient to elevate Abeta1-42/43, supporting a gain-of-function activity as the result of the PS1 mutation.

We report the characterization of Gsh-1, a novel murine homeobox gene. Northern blot analysis revealed a transcript of approximately 2 kb in sue present at embryonic days 10.5, 11.5, and 12.5 of development. The cDNA sequence encoded a proline rich motif, a polyalanine tract, and a homeodomain with strong homology to those encoded by the clustered Hox genes. The Gsh-1 expression pattern was determined for days E8.5 to E13.5 by whole mount and serial section in situ hybridizations. Gsh-1 transcription was restricted to the central nervous system. Expression is present in the neural tube and hindbrain as two continuous, bilaterally symmetrical stripes within neural epithelial tissue. In the mesencephalon, expression is seen as a band across the most anterior portion. There is also diencephalon expression in the anlagen of the thalamus and the hypothalamus as well as in the optic stalk, optic recess, and the ganglionic eminence. Moreover, through the use of fusion proteins containing the Gsh-I homeodomain, we have determined the consensus DNA binding site of the Gsh-1 homeoprotein to be GCT/cA/,ATTAG/A. 0 1995 Wiley-Liss, Inc.

We have cloned and sequenced human and bovine cDNAs for the beta subunit of the ATP synthase (ATP-syn beta), a nuclear DNA (nDNA) encoded oxidative phosphorylation (OXPHOS) gene. The two cDNAs were found to share 99% amino acid homology and 94% nucleotide homology. The evolutionary rate of ATPsyn beta was then compared with that of two mitochondrial DNA (mtDNA) ATP synthase genes (ATPase 6 and 8), seven other mtDNA OXPHOS genes, and a number of nuclear genes. The synonymous substitution rate for ATPsyn beta proved to be 1.9 x 10(-9) substitutions per site per year (substitutions x site-1 x year-1) (SSY). This is less than 1/2 that of the average nDNA gene, 1/12 the rate of ATPase 6 and 8, and 1/17 the rate of the average mtDNA gene. The synonymous and replacement substitution rates were used to calculate a new parameter, the "selective constraint ratio". This revealed that even the most variable mtDNA protein was more constrained than the average nDNA protein. Thus, the high substitution mutation rate and strong selective constraints of mammalian mtDNA proteins suggest that mtDNA mutations may result in a disproportionately large number of human hereditary diseases of OXPHOS.

We present an initial characterization of the murine Gsh‐4 gene which is shown to encode a LIM‐type homeodomain. Genes in this category are known to control late developmental cell‐type specification events in simpler organisms. Whole mount and serial section in situ hybridizations show transient Gsh‐4 expression in ventrolateral regions of the developing neural tube and hindbrain. Mice homozygous for a targeted mutation in Gsh‐4 suffer early postnatal death resulting from immature lungs which do not inflate. Prenatal administration of progesterone and glucocorticoid, to extend gestational term and accelerate maturation, resulted in lung inflation at birth. Nevertheless, the hormonally treated mutants generally failed to survive beyond an hour after birth, due to ineffective breathing efforts. It is concluded that Gsh‐4 plays a critical role in the development of respiratory control mechanisms and in the normal growth and maturation of the lung.