Abstract:Despite intensive studies of muscular dystrophy of chicken, the responsible gene has not yet been identified. Our recent studies mapped the genetic locus for abnormal muscle (AM) of chicken with muscular dystrophy to chromosome 2q using the Kobe University (KU) resource family, and revealed the chromosome region where the AM gene is located has conserved synteny to human chromosome 8q11-24.3, where the beta-1 syntrophin (SNTB1), syndecan 2 (SDC2) and Gem GTPase (GEM) genes are located. It is reasonable to assume those genes might be candidates for the AM gene. In this study, we cloned and sequenced the chicken SNTB1, SDC2 and GEM genes, and identified sequence polymorphisms between parents of the resource family. The polymorphisms were genotyped to place these genes on the chicken linkage map. The AM gene of chromosome 2q was mapped 130 cM from the distal end, and closely linked to calbindin 1 (CALB1). SNTB1 and SDC2 genes were mapped 88.5 cM distal and 27.6 cM distal from the AM gene, while the GEM gene was mapped 18.5 cM distal from the AM gene and 9.1 cM proximal from SDC2. Orthologues of SNTB1, SDC2 and GEM were syntenic to human chromosome 8q. SNTB1, SDC2 and GEM did not correspond to the AM gene locus, suggesting it is unlikely they are related to chicken muscular dystrophy. However, this result also suggests that the genes located in the proximal region of the CALB1 gene on human chromosome 8q are possible candidates for this disease.

Our previous studies revealed that the genetic locus for chicken muscular dystrophy of abnormal muscle (AM) mapped to chromosome 2q, and that the region showed conserved synteny with human chromosome 8q11-24.3. In the current study, we mapped the chicken orthologues of genes from human chromosome 8q11-24 in order to identify the responsible gene. Polymorphisms in the chicken orthologues were identified in the parents of the resource family. Twenty-three genes and expressed sequence tags (ESTs) were mapped to chicken chromosome 2 by linkage analysis. The detailed comparative map shows a high conservation of synteny between chicken chromosome 2q and human chromosome 8q. The AM locus was mapped between [inositol(myo)-1(or4)-monophosphatase 1] (IMPA1) gene and [core-binding factor, runt domain, alpha-subunit 2; translocated to 1; cyclin D-related] (CBFA2T1) gene. The genes located between IMPA1 and CBFA2T1 are the most likely candidates for chicken muscular dystrophy.

Nylon 6 films were prepared by gelation/crystallization from solutions and by molding from melt state. The resultant gel and melt films were elongated in a hot oven at 205'C under nitrogen. As co-solvent mixtures in preparing gel films, the formic acid/chloroform compositions studied were 100/0, 75/25, and 50/50. The mechanical properties of the gel films were hardly affected by composition but the gel film with the 75/25 composition could be readily elongated in comparison with those with the 100/0 and 50/50. The Young's moduli and the tensile moduli for all the specimens are less than 5 and 0.15 GPa, respectively. The values of the Young's moduli are much lower than the crystal lattice modulus (183 GPa) of nylon 6. To determine the reason for the poor mechanical properties of these specimens, the morphological properties of the gel film with the 75/25 composition, as an example, were investigated in comparison with those of the melt film by using wide angle X-ray diffraction, small angle X-ray scattering, and small angle light scattering. Deformation was found to be independent of a crystal transformation from a folded to a fibrous type and the preferential orientation of the crystal fiber axis (the b-axis) is mainly due to the rotation of crystallites leading to taut tie molecules. This mechanism hampers ultradrawing of nylon 6 films to realize high modulus and high strength.

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