Co-occurrences of polymorphic heterochromatin regions of chromosomes and effect on reproductive failure

Although the polymorphic heterochromatin regions of chromosomes (heteromorphisms) have been extensively studied for their phenotypic effects on humans, co-occurrences of chromosome 1, 9, 16 and Y heteromorphisms and of acrocentric variants have never been studied on humans with an objective scoring system. Here we compared the frequencies of individual heteromorphisms on a total of 602, 768 and 224 patients with the indications of infertility, recurrent miscarriage and in vitro fertilization (IVF) failure, respectively and on 272 controls. Then we examined whether there were significant co-occurrences between heteromorphisms within and between the groups. There were no statistically significant differences in the frequencies of heteromorphisms between the groups. Both statistically significant and non-significant correlations were observed within the non-acrocentric and certain acrocentric heteromorphisms in each group. When these co-occurrences were examined between the groups, a 2.2 fold increased risk of IVF failure in males in the presence of either chromosome 13 or chromosome 21 variants was observed (95 %CI:1.1–4.2). We conclude that the simultaneous manifestations of heteromorphisms have no effect on reproductive failure. There seems to be a correlation between the non-acrocentric heteromorphisms (1qh+, 9qh+, 16qh + and Yqh+/-), which might be the result of complex interactions of formation of these heterochromatin regions. The correlations observed between certain acrocentric chromosomes might be related to satellite association and nucleolus formation. The increased risk observed in males with IVF failure in the presence of either chromosome 13 or 21 variants should be interpreted cautiously due to the heterogeneity of the group.     

Karyotypic analysis of <Emphasis Type="Italic">Skimmia japonica</Emphasis> (Rutaceae) and related species

A karyotypic analysis of three species of Skimmia (Rutaceae) in East Asia was performed that examined 88 individuals from 53 localities. Chromosome numbers of S. japonica, S. reevesiana and S. arisanensis were 2n=30, 31, 32 (=30+0−2B), 2n=60 and 2n=60, respectively. The chromosome number of S. arisanensis was reported for the first time. All species had a large chromosome pair or quartet (the first pair or quartet) with a median–submedian centromere in the karyotype. In S. japonica the arm ratio of this first pair was considerably variable and showed a geographical pattern. In the northern half of the distribution range, Sakhalin, Hokkaido, Honshu, Shikoku and part of Kyushu, the arm ratio was 1–1.2, while in the southern half, part of Kyushu, Ryukyu and Taiwan, the arm ratio was very variable and ranged from 1.2 to 2.4. In S. japonica the first pair was sometimes rather heteromorphic; however, the heteromorphism was not related to sex of the plant.