L. Molteni

Cattle rob(1;29) originating from complex chromosome rearrangements as revealed by both banding and FISH-mapping techniques

Sixteen carriers of rob(1;29) (one of which was homozygous) from six different breeds (four Italian and two Portuguese), two heterozygous carriers of rob(26;29), three river buffaloes and two sheep were cytogenetically investigated in this study by using banding and FISH-mapping techniques (the latter only in cattle and river buffalo). Single- and dual- colour FISH were used with bovine probes containing both INRA143 (mapping proximally to BTA29) and bovine satellite (SAT) DNA SAT I, SAT III and SAT IV (mapping at the centromeric regions of cattle chromosomes). The combined use of these probes, the comparison of rob(1;29) with the dicentric rob(26;29) and with both river buffalo and sheep chromosomes (biarmed pairs) allowed us to hypothezise that rob(1;29) originated from complex chromosomal rearrangements through at least three sequential events: (a) centric fusion with the formation of a dicentric chromosome; (b) formation of a monocentric chromosome with loss of SAT I from both BTA1 and BTA29, most of SAT IV from BTA29 and, probably, some repeats of SAT III from BTA1; (c) double pericentric inversion or, more probably, a chromosome transposition of a small chromosome segment containing INRA143 from proximal p-arms to proximal q-arm of the translocated chromosome.

A case of azoospermia in a bull carrying a Y-autosome reciprocal translocation

During normal cytogenetic investigations on the Chianina cattle (BTA) breed, a normal looking young bull was found to carry an abnormal Y chromosome which was a product of a reciprocal translocation between chromosomes Y and 9. This was revealed by both CBA- and RBG-banding techniques and was clearly confirmed by FISH-mapping analysis with IDVGA50 (which paints the complete Yq arm in a normal Y), as well as with AMD1, CGA, IGF2R (mapping to BTA9q16, BTA9q22 and BTA9q27→q28, respectively) and SRY (mapping to normal BTAYq23). Analysis on sperm from four different samples revealed azoospermia in the carrier, indicating that the rcp(Y;9) induces sterility in the bull.

Mutations in the RSPO1 coding region are not the main cause of canine SRY-negative XX sex reversal in several breeds.

This report details a case of SRY-negative XX sex reversal in a mixed breed dog and surveys affected dogs of several breeds for mutations in RSPO1 coding regions. Genomic DNA from the mixed breed case was evaluated for mutations in candidate genes. Sequencing identified a homozygous G to A transition in RSPO1 exon 4 that changes a highly conserved amino acid codon in the thrombospondin domain. The possibility that this was a single nucleotide polymorphism (SNP) could not be excluded by genotyping family members. Therefore, the coding region of RSPO1 was sequenced in a survey of affected dogs, which identified a T to C transition (exon 3) in some, the above G to A transition (exon 4) in others, and no change in the remaining affected dogs. Genotypes at these base pair positions were not uniquely associated with the affected phenotype in any breed, indicating the identified transitions are most likely SNPs, not causative mutations for this canine disorder. However, the possibility that polymorphisms play a modifier role, such as changing threshold or severity of phenotypic expression in a mixed breed dog, cannot be excluded. This study emphasizes the importance of canine pedigree, breed, and population studies in evaluating candidate mutations.

Characterization of a balanced reciprocal translocation, rcp(9;11)(q27;q11) in cattle

Cytogenetic analysis of a phenotypically normal young bull from Marchigiana breed revealed the presence of an abnormal karyotype. The observation of longer and smaller chromosomes than BTA1 and BTA29, respectively in all metaphases suggested the presence of a reciprocal translocation. RBG-banding confirmed this hypothesis revealing the involvement of BTA9 and BTA11. FISH analyses using cattle-specific BAC clones (474A12 and 293G09 for BTA9; 035D03 for BTA11) identified rcp(9;11)(q27;q11) in the two regions affected. Moreover analyses performed on both parents established the ‘de novo’ origin of the anomaly. Comparison with human homologue sequences (HSA6q24.3→q25.3 for BTA9q27 and HSA2q11.1→q12.1 for BTA11q11) revealed that both breakpoint regions are gene rich as up to date at least 200 genes have been localized in these regions. Thus, further analyses are required to identify the sequences disrupted by the breakpoints and to verify their consequences on rcp carrier phenotype.

A new balanced autosomal reciprocal translocation in cattle revealed by banding techniques and human-painting probes

Three hundred and twenty-two (264 males and 58 females), randomly sampled Grey Alpine cattle individuals from Northeastern Italy, were investigated cytogenetically by both conventional chromosome staining and R-banding. Two hundred and eighty-one (87%) individuals had a normal karyotype and 41 (13%) carried chromosomal aberrations such as (a) rob(1;29) in two individuals, (b) rob(26;29) in 36 individuals, (c) XX/XY-chimerism in two individuals, and (d) an abnormally long chromosome in one individual. All these aberrations except (d) have been described before. GBG-, RBG-, CBA-banding and sequential GBG/CBA- and RBG/CBA-banding techniques revealed that the abnormally long chromosome was the result of a reciprocal translocation between chromosomes 1 (q21→qter) and 5 (q11→q33), as confirmed also by chromosome painting with human chromosome 3 and 12 probes. The dam of the carrier bull carried the same translocation, while the grandam showed a normal karyotype. Since the sire of the dam was not available for study, no conclusion about the origin of the chromosome translocation could be drawn. The carrier bull was eliminated because of poor fertility. The dam had three other calves, which all were chromosomally normal. On average the dam had to be served 2.5 times (breed average was 1.2) to be in calf.

New cases of XXY constitution in cattle

The present paper describes two cases of an XXY condition in Chianina cattle. Both young bulls were routinely investigated cytogenetically before entering progeny test stations. Every cell examined in the blood cell cultures showed an XXY constitution. The histological study of the gonads, performed on only one bull, showed degradation of the seminiferous tubules. Only Sertoli cells and hyperplastic interstitial cells were observed.

A new case of reciprocal translocation in a young bull: rcp(11;21)(q28;q12)

Routine cytogenetic investigations of the Chianina cattle (BTA) breed revealed the presence of longer and smaller chromosomes than the largest (BTA1) and smallest (BTA29) chromosomes in the cells of a young, normal-looking bull used for reproduction. Application of both RBA-banding and Ag-NOR techniques, as well as the use of the FISH technique and specific molecular markers of both BTA11 (IL1B, ASS and LGB) and BTA21 (SERPINA and D21S45) established that these two abnormal chromosomes were the product of a reciprocal translocation between BTA11 and BTA21. Both der(11) and der(21) were C-band positive and the chromosome regions affected were rcp(11;21)(q28;q12). The young bull had a normal body conformation, including external genitalia, normal levels of testosterone (as in the control) and non-detectable levels of both 17 beta-estradiol and progesterone (as in the control). The animal never showed libido in the presence of both males and females in oestrus. After slaughter at 18 months, histological evaluation revealed normal organized testes, seminiferous tubules and epididymis but with poor proliferative germ cells consisting mainly of spermatogonia, middle pachytene spermatocytes and early spermatids with late spermatids and spermatozoa being very rare.

Ichthyosis in Chianina cattle

The oral mucosae of the lips and muzzle appeared histologically normal. Mitotic chromosomes were visualised with conventional staining and RBA-banding from non-synchronised cultures of peripheral blood lymphocytes of the affected calves and their relatives (De Grouchy and others 1964, Dutrillaux and others 1973). No abnormality was detected in either the structure or the number of chromosomes. Genealogical data from the Chianina Breed Stud Book, from the Associazione Nazionale Allevatori Bovini Italiani da Carne (ANABIC), were collected to analyse the pedigrees of the two affected animals and of nine other newborn Chianina calves showing the same condition (Fig 3). Wherever possible, blood samples were collected from the affected animals and their sires, dams and siblings. Parentage relationships were verified by microsatellite analysis with StockMarks for Cattle Paternity PCR typing kits (Applied Biosystems). Forty-nine animals of the familial group were evaluated. Analysis of the pedigree information revealed that all clinical cases were generated by consanguineous matings. In particular, three bulls were acknowledged as being disease carriers: bulls 23, 30 and 34 (Fig 3). Bull 23 sired three affected male calves (26, 28 and 48) and two healthy female calves (31 and 35); bull 30 sired two affected male calves (27 and 49) and two healthy calves, one male (34) and one female (46); and bull 34 sired six affected calves, four males (38, 40, 41 and 47) and two females (43 and 44) and four healthy calves, three males (37, 42 and 45) and one female (39). None of the carIchthyosis in Chianina cattle

Reciprocal translocations in cattle: frequency estimation

Chromosomal anomalies, like Robertsonian and reciprocal translocations, represent a big problem in cattle breeding as their presence induces, in the carrier subjects, a well-documented fertility reduction. In cattle, reciprocal translocations (RCPs, a chromosome abnormality caused by an exchange of material between non-homologous chromosomes) are considered rare as to date only 19 reciprocal translocations have been described. In cattle, it is common knowledge that the Robertsonian translocations represent the most common cytogenetic anomalies, and this is probably due to the existence of the endemic 1;29 Robertsonian translocation. However, these considerations are based on data obtained using techniques that are unable to identify all reciprocal translocations, and thus, their frequency is clearly underestimated. The purpose of this work is to provide a first realistic estimate of the impact of RCPs in the cattle population studied, trying to eliminate the factors that have caused an underestimation of their frequency so far. We performed this work using a mathematical as well as a simulation approach and, as biological data, we considered the cytogenetic results obtained in the last 15 years. The results obtained show that only 16% of reciprocal translocations can be detected using simple Giemsa techniques, and consequently, they could be present in no <0.14% of cattle subjects, a frequency five times higher than that shown by de novo Robertsonian translocations. This data is useful to open a debate about the need to introduce a more efficient method to identify RCP in cattle.

Chromosomal characterization of three centric fusion translocations in cattle using G-, R- and C-banding and FISH technique

Abstract Five cattle, two of the Podolian breed, two Grey Alpine, and one Chianina,all of which were heterozygous carriers of three centric fusion translocations(rob-l;29, rob-4;8, rob-25;27), underwent cytogenetic investigation. The use of G-, R- and C-banding patterns, combined with the FISH technique by using both type I molecular markers and some human chromosome painting probes, allowed the precise identification of chromosomes involved in the chromosomal abnormalities,compared to previous reports. While the chromosomes involved in the well known rob (1;29) were confirmed, BTA6 (not BTA4) was involved in the second translocation. Furthermore, BTA26 and BTA29 (not BTA25 and BTA27) were involved in the third translocation. C-banding patterns confirmed the mono-centric nature of rob (1;29) and revealed the dicentric nature of both rob(6;8) and rob(26;29). The importance of these marker chromosomes in bovid chromosome nomenclatures is also discussed.