Robertsonian translocation in Sykia Chalkidiki cattle

This is the first report on the Robertsonian 1/29 translocation in the Sykia Chalkidiki cattle breed. The characteristics of this endangered breed are described, and the possibilities of rescuing and exploiting the breed in a zootechnical sense are examined.     

A new case of Robertsonian translocation in cattle

A new Robertsonian translocation was found in several animals of the Blonde d'Aquitaine breed. The fused chromosome analyzed by G- and R-banding results from the fusion of chromosomes 21 and 27. C-banding suggests that the fused chromosome is dicentric.     

Segregation of chromosomes in sperm of Robertsonian translocation carriers

Robertsonian translocations are the most frequent structural chromosomal abnormalities in humans and can affect fertility, with various degrees of sperm alterations in men; or the pregnancy outcome of the carriers. The studies on meiotic segregation of chromosomes in sperm of Robertsonian translocation males find a majority of normal or balanced spermatozoa for the chromosomes related to the translocation (mean 85.42%; range 60-96.60%). Furthermore, recent studies suggest an interchromosomal effect. Studies on spermatozoa from translocation carriers, and in mouse models help the comprehension of the meiotic segregation mechanisms. Results of meiotic segregation analysis in man could be integrated in genetic counselling especially when assisted reproductive technology is required.     

Fertility effects of the 14;20 Robertsonian translocation in cattle

Superovulation and embryo collection procedures were used to study the effect of the 14;20 Robertsonian translocation on fertility and embryo viability. Karyotypes were successfully completed on cells from 77 of the 279 embryos prepared for such analysis. Embryos from 4 cows heterozygous for the translocation were studied. Two bulls with the same condition were studied by using their semen in artificial insemination of cows with normal karyotypes. The proportions of fertilized ova and transferable embryos were not different between cows with the 14;20 translocation and those with normal karyotypes, indicating that fertilization rates were not affected by the translocation. Twenty-two percent of the embryos which were karyotyped had an unbalanced karyotype and would theoretically not have survived to term. All of the theoretically predicted chromosome complements from such a translocation were observed as were three 58,XX,t karyotypes and a 58,XX karyotype. There was no difference in the percentage of embryos with abnormal karyotypes whether the cow or bull was the carrier. Results therefore indicate that fertility is rather severely impaired in carriers of the 14;20 translocation, as was observed with the 1;29 translocation, with most loss due to embryo mortality rather than a lowered conception rate.     

Robertsonian translocation in a Zebu bull

Karyotypes were prepared for ten Rahaji bulls using cultured peripheral blood lymphocytes. C-banded metaphases were prepared to identify the sex chromosomes and possible translocations. Out of the ten bulls, studied one bull had a 2n number of 59 chromosomes and carried a Robertsonian translocation. The possible importance of the Robertsonian translocation in Zebu cattle in Nigeria is discussed.     

Embryonic loss in superovulated cattle caused by the 1;29 Robertsonian translocation

The effect of the 1;29 Robertsonian translocation on fertility was studied using embryos resulting from matings of nine carrier cows and two carrier bulls. Embryos were collected from the following three mating groups utilizing superovulation: normal bull cross normal cow, normal bull cross translocation carrier cow, and translocation carrier bull cross normal cow. The proportion of ova which were fertilized did not vary among the groups, indicating that fertilization rates were not affected by the translocation. The translocation cows did yield fewer embryos on average than did cows with normal karyotypes, which may suggest ovulation rates are reduced (at least after superovulation attempts) in cattle carrying the 1;29 translocation. Twenty of 39 embryos successfully karyotyped had abnormal chromosome complements. All four of the theoretically predicted karyotypes and two additional abnormal combinations were found. Eight of 39 (20.5%) embryos karyotyped had unbalanced karyotypes which would have resulted in embryonic loss. The proportion of embryos with unbalanced karyotypes, was slightly higher when the cow (36%) carried the translocation than when the bull (19%) did. Results of this study indicate that fertility is impaired due to the presence of this translocation. The major loss in reproductive potential appears to be due to embryonic loss rather than fertilization failure.     

A new Robertsonian translocation in cattle, rob(15;25).

A new Robertsonian translocation, rob(15;25), was discovered in a Portuguese Barrosa cow. The animal (2n = 59,XX) was found by G- and R-banding to be a heterozygous carrier of a centric fusion translocation involving chromosomes 15 and 25. C-banding revealed the dicentric nature of this new centric fusion. Comparison of this new translocation with the well-known Robertsonian translocation rob(1;29), which is often found in the same breed, confirmed that two different chromosomes (25 and 29) were involved in the short arms of these two Robertsonian translocations.     

A Robertsonian translocation, rob(2;28), found in Vietnamese cattle

A new Robertsonian translocation, rob(2;28), was discovered in a local population of the Vietnamese Cattle. The animal (2n = 59, XY) was found by Q- and R-banding to be a heterozygous carrier of a centric fusion translocation involving chromosomes 2 and 28. FISH analysis using a bovine satellite I DNA probe demonstrated that the centromeric heterochromatin block of the rob(2;28) chromosome become much smaller than its ancestors suggesting a monocentric nature of this centric fusion. This is the first report identifying a Robertsonian translocation in Southeast Asian cattle by karyotyping of banded chromosomes.     

Homozygous Robertsonian translocations in a fetus with 44 chromosomes

Summary We report the unique finding of a human fetus with 44 chromosomes with homozygous 14;21 translocations. This fetus appeared phenotypically normal but the long-term neurodevelopmental outcome had this pregnancy continued could not be predicted. We speculate one 14;21 translocation was inherited from her father and one arose de novo being maternal in origin. A previous sibling with psychomotor retardation has an abnormal chromosome complement of 45,XX,dup(7)(q21pter), t(14;21)(p11;q11). The mother's underlying disease, systemic lupus erythematosis (SLE), and her prior chemotherapy may have contributed to the appearance of these chromosome aberrations. It is interesting that although 14;21 translocations are among the commonest structural chromosome rearrangements in man, there are no previous reports in newborn surveys of a child with 44 chromosomes resulting from the mating of two identical Robertsonian translocation carrier parents.     

Cytological identification of the chromosomes involved in Nishimura's rice translocation lines

During the past three decades, Nishimura's reciprocal translocation lines of rice have been used in rice cytogenetics to locate genes on chromosomes, to number extra chromosomes of trisomic series and to associate individual linkage groups with specific chromosomes. In this report, we present our identification of the chromosomes involved in 11 of Nishimura's translocation lines using both meiotic pachytene and mitotic prometaphase chromosome analysis. In addition, the numbering of the 12 linkage groups suggested by Nagao and Takahashi, and modified later by many workers, has been revised to agree with the numbering of the identified chromosomes.     

Robertsonian translocation and genetic counseling

A collaborative study on 92 Robertsonian translocations is analysed in relation with the methods of ascertainment, the type of rearrangement and potential imbalance of the anomaly. The results are useful in genetic counselling.