No induction of interchromosomal effect in male meiosis of Chinese hamsters with reciprocal translocations

Abstract

Chinese hamsters from five strains with reciprocal translocations, T(l;3)7Idr, T(l;3)8Idr, T(l;2)9Idr, T(7;9)16Idr, and T(l;5)17Idr, and a karyotypically normal strain, CHS/Idr, were used to look for an interchromosomal effect by chromosomal analysis of meiotic cells and one-cell embryos. The frequencies of nondisjunction at first meiosis in five normal ( + / + ) males, calculated by doubling the number of hyperhaploid cells, ranged from 0.43% to 1.33%, and there was no significant difference in frequency among individuals. On the other hand, the frequency of hyperhaploid cells in males heterozygous for each translocation ranged from 3.0% to 11.8%, and the frequency of hyperhaploid cells with an extra translocation-unrelated chromosome ranged from 0.2% to 0.4%, which is no different from that estimated from scoring of +/+ males at the second meiotic metaphase. In one-cell embryos from crosses between karyotypically normal females and male heterozygotes for T(l;2)9Idr and T(7;9)16Idr, 1.1% and 0.5% of embryos had an extra translocation-unrelated chromosome. Compared with the control, the frequency of meiotic nondisjunction showed no increase in male heterozygotes for the reciprocal translocations. Therefore, the results suggest that multivalents and rearranged chromosomes existing at first and second meiosis in male Chinese hamsters exert no influence on segregation of normal bivalents and chromosomes unrelated to the rearrangements.

Independent chromosome segregation and absence of interchromosomal effect at first meiotic division in male Chinese hamsters heterozygous for two reciprocal translocations

“…Chromosomal data of karyotypically normal males from an inbred strain CHS/Idr, which were described in a previous study (Sonta and Kitayama, 1991), were used as controls. The translocation strains were all originated from the offspring of X-irradiated hamsters of the CHS/ldr strain.…”

“…In experimental mammals, there have been few studies on interchromosomal effects by direct analysis of meiotic cells as well as fetuses (Ford and Evans, 1973;Wauben-Penris et al, 1983: Sonta andKitayama, 1991). In this study, we investi gated chromosome segregation and interchromosomal effects in male Chinese hamsters heterozygous for two reciprocal translocations.…”

Contribution of chromosomal imbalance to sperm selection and pre-implantation loss in translocation-heterozygous Chinese hamsters

“…during first and second meiosis, the presence of rearranged chromosomes exerts no influence on the segregation of chromosomes unrelated to the rearrangement (Sonta and Kitayama, 1991;Sonta et al, 1995). This is a distinct advantage over Robertsonian translocations in mice.…”

“…We conducted experiments since 1976 to obtain animals with various structurally abnormal chromosomes produced by X irradiation (Sonta and Oishi, 1982;Sonta and Kitayama, 1991;. The Chinese hamsters used in our study were in the 17-24 th generations of inbreeding.…”

“…By crossing translocation heterozygotes to normal partners, we compared the frequencies of 1-cell embryos with each possible karyotype with the expected frequencies estimated by MII scoring to detect selection against chromosomally abnormal sperm. Young adult (6-to 9-month-old) Chinese hamsters from a karyotypically normal strain, CHS/Idr, were mated to young adults from the 18 translocation stocks (Table 2) (Sonta and Oishi, 1982;Sonta et al, 1987Sonta et al, , 1991. Chromosomal constitutions of derivatives from the first meiotic quadrivalents in these 18 translocation heterozygotes were identified in MII cells as well as in pronuclei of fertilized ova.…”