The utility of chromosome microdissection in clinical cytogenetics: a new reciprocal translocation in sheep.

Local sheep breeders and scientists in Italy cooperate and conduct research on the genetic improvement of autochthonous genetic types (AGTs) by various approaches, including a cytogenetic breeding selection since 2011. The Laticauda sheep (Ovis aries, 2n = 54) breed is one of the AGTs reared in the Campania region (southern Italy). Performing cytogenetic analyses, we have detected and described a novel reciprocal translocation in a Laticauda sheep identified as 54,XX t(18;23)(q14;q26). Our data support recurring appeals that suggest the regular performance of cytogenetic analyses for monitoring genetic health of livestock species. In total, 5 cases of reciprocal translocations in sheep are known, including the new case. None of them has any phenotypic effect on the living offspring. However, affected animals are characterized by sterility or have a low fertility which can have an effect on breeding success and on economical balance. Presence and kind of the described novel chromosomal aberration were detected by performing CBA-banding and FISH mapping with telomeric probes. RBA-banding allowed the karyotyping of sheep chromosomes and the identification of aberrant chromosomes and regions involved in the new reciprocal translocation. Whole chromosome painting (WCP) probes received from equivalent chromosomes in cattle and the derivative sheep chromosome 18 confirmed the cytogenetic data. This way, our study underlined both the importance of WCP probes by chromosome microdissection and a new way to use WCP probes directly generated from derivative chromosomes.