Polymelia associated with frequent chromosome breaks in a heifer

Abstract

FIG 2: Metaphase spread with chromosome breaks (arrows), showing (a) a single break in an autosome and (b) three breaks, one in an X chromosome and two in autosomesPOLYMELIA is a rare congenital defect characterised by the presence of a supernumerary limb at different locations on the body. Depending on the body region, polymelia has been classified as notomelia, cephalomelia, thoracomelia and pygomelia (Kim and others 2001). The phenomenon of polymelia is usually associated with other congenital defects such as polydactyly (extra fingers or toes) or the presence of additional and often underdeveloped bones (Murondoti and Busayi 2001). In most cases, the extra limb is shorter and devoid of muscle tissue. The physiological attributes of the affected animal, including temperature, pulse and respiration rate, are usually normal (Hirsbrunner and others 2002). This short communication describes polymelia in a heifer, associated with frequent chromatid/chromosome breaks observed in lymphocytes cultured in vitro.A black-and-white heifer, genetically 62·5 per cent Holstein-Friesian, was born with four normal legs and one extra limb localised in a shoulder girdle between the scapulas. The supernumerary limb was smaller than the normal legs, was bent at the carpal joint and had a terminal hoof. It hung down on the left side of the animal (Fig 1a). The extra limb was attached to an underdeveloped additional scapula, which was connected to the thoracic vertebrae. The animal underwent surgery on two occasions at three and four months of age. During the first operation the additional leg was removed at the shoulder joint. During the second operation, which was performed due to unsuccessful wound healing, only a part of the extra scapula was removed at the neck of the scapula; the whole scapula was not removed due to the risk of injury to the vertebral column.The skeleton of the additional limb, according to anatomical nomenclature (Dyce and others 1987), consisted of the stylopodium (humerus), zeugopodium (radius and ulna) and autopodium, including the basipodium (carpal bones), metapodium (metacarpal bones) and acropodium (proximal, middle and distal phalanges) (Fig 1b). The stylopodium consisted of a single long bone with distinguishable epiphysial cartilage of the proximal epiphysis and three unfused skeletal elements that made up the metaphysis. The diaphysis of the stylopodium, near the epiphysis, was laterally flattened. The appearance of this bone resembled a humerus. The zeugopodium included one long bone with a cleft in the diaphysis; however, the epiphyisis and metaphysis were jointed. It was not possible to conclude whether this bone was an element of a thoracic or pelvic limb. The basipodium consisted of carpal bones that were fused in two blocks not resembling the tarsal bones (there was no talus or calcaneus). The metapodium of the extra limb had features that were not typical of this segment of the autopodium in cattle. Two bones were partially fused together (a massive one and a very thin underdeveloped bone). ...

Chromosome Instability in a Calf with Amelia of Thoracic Limbs

“…4 Another case of a malformed calf affected with polymelia and a high incidence of chromosome breaks was described recently. 15 On the other hand, chromosome instability (Fig. 4A, B, D), and 2 micronuclei localized in a close vicinity of the nucleus (Fig.…”

Cytogenetic screening of livestock populations in Europe: an overview

“…In both cases, frequent chromatid and chromosome breaks were observed (Szczerbal et al, 2006;Nowacka et al, 2007). Screening programs in sheep and goats.…”

Notomelia in a piglet (Sus scrofa): Case report and review of the literature

“…Notomelia is not uncommon in cattle. In contrary, cattle has been diagnosed in various breeds, including Brahman (Fourie, ), Korean native (Alam et al, ; Islam et al, ; Kim et al, ), Holstein‐Friesian (Hirsbrunner, Keller, & Dolf, ; Murihead, Pack, & Radke, ; Nowacka et al, ), Angus (Denholm, ), Jersey (Barua et al, ), Simmental (Özak, Nisbet, & Yardimci, ). The majority of the notomelia in ruminants affects the female animals (Table ).…”

“…However, the aetiology of polymelia differs by cattle breed and is the result of genetic variants at more than one locus. A bovine polymelia case has been studied cytogenetically (Nowacka et al, ). The chromosome breaks observed in the studied calf reflect genome instability.…”