Fgf10 is essential for limb and lung formation.

The interactions between fibroblast growth factors (FGF) and their receptors have important roles in mediating mesenchymal-epithelial cell interactions during embryogenesis. In particular, Fgf10 is predicted to function as a regulator of brain, lung and limb development on the basis of its spatiotemporal expression pattern in the developing embryo. To define the role of Fgf10, we generated Fgf10-deficient mice. Fgf10-/- mice died at birth due to the lack of lung development. Trachea was formed, but subsequent pulmonary branching morphogenesis was disrupted. In addition, mutant mice had complete truncation of the fore- and hindlimbs. In Fgf10-/- embryos, limb bud formation was initiated but outgrowth of the limb buds did not occur; however, formation of the clavicles was not affected. Analysis of the expression of marker genes in the mutant limb buds indicated that the apical ectodermal ridge (AER) and the zone of polarizing activity (ZPA) did not form. Thus, we show here that Fgf10 serves as an essential regulator of lung and limb formation.

Aberrant growth plate development in VDR/RXR gamma double null mutant mice.

VDR forms heterodimers with one of three RXRs, RXR alpha, RXR beta, and RXR gamma, and it is thought that RXR ligands can also modulate the trans-activation function of VDR/RXR heterodimers. In the present study we generated VDR/RXR gamma double null mutant mice to examine the convergent actions of vitamin D and vitamin A signaling and to explore the possibility of a functionally redundant VDR. Although RXR gamma(-/-) mice exhibited no overt abnormalities, VDR(-/-)/RXR gamma(-/-) mice appeared similar to VDR(-/-) mice, showing features typical of vitamin D-dependent rickets type II, including growth retardation, impaired bone formation, hypocalcemia, and alopecia. However, compared to VDR(-/-) mice, growth plate development in VDR(-/-)/RXR gamma(-/-) mutant mice was more severely impaired. Normalizing mineral ion homeostasis through dietary supplementation with high calcium and phosphorous effectively prevented rachitic abnormalities, except for disarranged growth plates in VDR(-/-)/RXR gamma(-/-) mutant mice, and alopecia in both VDR(-/-) and VDR(-/-)/RXR gamma(-/-) mutant mice. Histological analysis of VDR(-/-)/RXR gamma(-/-) growth plates revealed that development of the hypertrophic chondrocytes was selectively impaired. Thus, our findings indicated that the combined actions of VDR- and RXR gamma-mediated signals are essential for the normal development of growth plate chondrocytes, and raised the possibility that a functionally redundant VDR is present on chondrocytes as a heterodimer with RXR gamma.

Isolation and characterization of eight microsatellite loci from the longheaded eagle ray, Aetobatus flagellum (Elasmobranchii, Myliobatidae).

The longheaded eagle ray, Aetobatus flagellum feeds mainly on bivalves, and there have been some indications that the current reduction in the bivalve population in southern Japan may be due to an increase in the number of longheaded eagle rays. Consequently, the 'predator control programme' for reducing the longheaded eagle ray population was established in 2001 in Japan. For studying the population genetics of the longheaded eagle ray, we isolated eight polymorphic microsatellite loci (two to six alleles per locus; expected heterozygosity, 0.172-0.700) from this species.

PERMANENT GENETIC RESOURCES: Isolation and characterization of nine microsatellite loci from the chub mackerel, Scomber japonicus (Perciformes, Scombridae).

The stock abundance of the chub mackerel Scomber japonicus - a very important species for fisheries, particularly in Japan - in the Pacific Ocean off Japan has remained at a low level. For studying the population genetics of the chub mackerel, we isolated nine polymorphic microsatellite loci (12-31 alleles/locus; expected heterozygosity, 0.762-0.983) from this species. Cross-species amplification indicated that eight of the nine microsatellite loci in the blue mackerel S. australasicus were polymorphic and functional.

Intervarietal and interspecific chimera formation by in vitro graft-culture method in Brassica.

An efficient chimera formation method by tissue culture combined with grafting was studied in Brassica. Cabbage cultivars "Ruby-ball" and "YR-ranpou" (Brassica oleracea) were used for intervarietal chimera formation. Seven-day-old seedlings leaving one of two cotyledons were approach-grafted and cultured in vitro (AGSC method). Chimeric shoots were obtained by the subculture of directly growing chimeric leaves (DGCL) from grafted part and cross-cut section of the united part after the graft culture. These were rooted and grown to complete chimera. An approach-grafted culture method was also available for interspecific chimera formation between "Komatsuna" (B. campestris) and "Ruby-ball" (B. oleracea), resulting in 20% formation per culture. Interspecific chimeras were identified as complex and peripheral-sectorial type by microscopic observation and the electrophoretic analysis of acid phosphatase isozyme pattern. The AGSC method was more effective than the usual Winkler's graft method and a simple mixed culture of heterogeneous cells or tissues.