Disruption of Genetic Interaction Between Two Autosomal Regions and the X Chromosome Causes Reproductive Isolation Between Mouse Strains Derived From Different Subspecies

Reproductive isolation that initiates speciation is likely caused by incompatibility among multiple loci in organisms belonging to genetically diverging populations. Laboratory C57BL/6J mice, which predominantly originated from Mus musculus domesticus, and a MSM/Ms strain derived from Japanese wild mice (M. m. molossinus, genetically close to M. m. musculus) are reproductively isolated. Their F(1) hybrids are fertile, but successive intercrosses result in sterility. A consomic strain, C57BL/6J-ChrX(MSM), which carries the X chromosome of MSM/Ms in the C57BL/6J background, shows male sterility, suggesting a genetic incompatibility of the MSM/Ms X chromosome and other C57BL/6J chromosome(s). In this study, we conducted genomewide linkage analysis and subsequent QTL analysis using the sperm shape anomaly that is the major cause of the sterility of the C57BL/6J-ChrX(MSM) males. These analyses successfully detected significant QTL on chromosomes 1 and 11 that interact with the X chromosome. The introduction of MSM/Ms chromosomes 1 and 11 into the C57BL/6J-ChrX(MSM) background failed to restore the sperm-head shape, but did partially restore fertility. This result suggests that this genetic interaction may play a crucial role in the reproductive isolation between the two strains. A detailed analysis of the male sterility by intracytoplasmic sperm injection and zona-free in vitro fertilization demonstrated that the C57BL/6J-ChrX(MSM) spermatozoa have a defect in penetration through the zona pellucida of eggs

Brain Metastasis from Hepatocellular Carcinoma after Radical Hepatectomy

Brain metastasis from hepatocellular carcinoma (HCC) is a rare, yet perplexing problem in patients with cancer. We report on 5 patients with metastasis of HCC to the brain after radical hepatectomy. Intrahepatic recurrence occurred in 3 patients, and distant metastasis to sites other than the brain was observed in 3 patients (lung, 2; bone, 1). The symptoms for brain metastasis included headache, hemiparesis, and vomiting. Hemorrhage was found in 4 of 5 patients. All patients had a single nodular lesion in the brain. The alpha-fetoprotein levels were more than 10,000 ng/ml in 4 patients. Two patients underwent surgical resection, 1 received cranial irradiation, and 2 were administered corticosteroids. The interval between diagnosis of the primary cancer and detection of brain metastasis ranged from 2 to 54 months. The mean survival period was only 3 months after diagnosis of brain metastasis. All 5 patients died of neurologic causes. Because no effective treatment for brain metastasis from HCC is available, further study is needed