Human Chromosome 10 loci map to three different sheep chromosomes

The interleukin 2 receptor (IL2RA), a human Chromosome (Chr) 10p locus, was mapped to sheep Chr 13q12-q15 by in situ hybridization. Two loci from human Chr 10q, cytochrome P450 subfamily XVII (CYP17) and the tachykinin 2 receptor (TAC2R), were assigned to sheep Chrs 22q21-q23 and 25q14-q23 respectively. The assignment of IL2RA allows the provisional assignment of the previously unassigned sheep syntenic group U15 to sheep Chr 13. Sheep linkage group 5 is predicted to be located on sheep Chr 25 on the basis of the TAC2R assignment.     

Physical mapping confirms that sheep chromosome 10 has extensive conserved synteny with cattle chromosome 12 and human chromosome 13

The following loci, on human chromosome 13, have been newly assigned to sheep chromosome 10 using chromosomally characterized sheep-hamster cell hybrids: gap junction protein, beta 2, 26 kDa (connexin 26) (GJB2); gap junction protein, alpha 3, 46 kDa (connexin 46) (GJA3), and esterase D/formylglutathione hydrolase (ESD). This assignment of ESD is consistent with comparative mapping evidence, but not with an earlier report of it on sheep chromosome 3p26-p24. Cell hybrid analysis confirmed the location of another human chromosome 13 locus, retinoblastoma 1 (including osteosar-coma) (RBI), and the anonymous ovine genomic sequence RP11 on sheep chromosome 10. Isotopic in situ hybridization was used to regionally localize RP11 on to sheep 10q15-q22. The location of microsatellites AGLA226, OarDB3, OarHH41, OarVH58, and TGLA441, previously assigned to sheep chromosome 10 by linkage analysis, was confirmed by polymerase chain reaction using the cell hybrid panel. These mapping data provide further evidence that sheep chromosome 10 is the equivalent of cattle chromosome 12, and that these chromosomes show extensive conserved synteny with human chromosome 13.     

Sheep linkage mapping: RFLP markers for comparative mapping studies

Restriction fragment length polymorphisms (RFLPs) detected using cDNA probes for conserved genes provide an important set of markers that anchor or link syntenic groups in a range of divergent mammalian species. DNA probes from sheep, cattle, pig, human and mouse were screened against sheep DNA samples and 24 new RFLP markers for sheep were identified. Among the loci tested, 22 had a homologue that has been mapped in humans. An RFLP for fibronectin (FN1) was linked to α-inhibin (INHA) at a distance of 5cM. The FN1 locus has been assigned to sheep chromosome 2q41–q44 and linkage between FN1 and INHA assigns INHA to the same chromosome in sheep. In addition to the new loci reported here, 28 RFLPs have been published previously by this group and these are collated together with RFLPs published from other laboratories. RFLPs have been reported for 86 loci in sheep. Fifty-four loci have been mapped to 16 different chromosomes.     

Regional Assignment of Conserved Reference Loci Anchors Unassigned Linkage and Syntenic Groups to Ovine Chromosomes

Seven loci that have been previously mapped to human and mouse chromosomes have now been regionally assigned to six sheep chromosomes. Nerve growth factor β (NGFB), antigen CD3 ζ polypeptide (CD3Z), inhibin β A (INHBA), estrogen receptor (ESR), rhodopsin (RHO), insulin-like growth factor 2 (IGF2), and myelin basic protein (MBP) were mapped by in situ hybridization to sheep chromosomes 1p24-p21, 1p14-p11, 4q26-q31, 8q25-q27, 19q23-qter, 21q21-qter, and 23q11-q12.3, respectively. ESR, RHO, IGF2, and MBP are the first markers to be assigned to their respective sheep chromosomes. These new data allow the previously unassigned sheep linkage groups H, J, K, and S to be provisionally assigned to chromosomes 21, 19, 4, and 8, respectively. The unassigned sheep syntenic groups U8 and U13 are provisionally assigned to sheep chromosomes 8 and 21, respectively. The new assignments support the emerging picture that there is extensive conservation of human chromosomal segments in the sheep and cattle genomes. The position of another evolutionary breakpoint on human chromosome 1q is suggested.     

The loci for parathyroid hormone and beta-globin are closely linked and map to chromosome 15 in cattle

We report linkage of the loci for beta-globin (HBB) and parathyroid hormone (PTH) in cattle and the assignment of both loci to the bovine chromosome region 15q13-q23. Linkage was analyzed in a family of paternal half-sibs by the use of restriction fragment length polymorphisms detected with bovine probes derived from the HBB and PTH genes. The HBB polymorphism was detected by digestion with restriction endonuclease HindIII and the PTH polymorphism with MspI. The maximum lod score for linkage of PTH with HBB was zeta = 4.52 at theta = 0, suggesting very close linkage of the two loci. The finding of the PTH/HBB linkage is corroborated by the physical assignment of both loci to the region 15q13-q23 by in situ hybridization with bovine genomic probes derived from PTH and HBB, respectively. Since HBB and PTH are syntenic in man and mouse, these results in cattle represent another example of conservation of synteny in the evolution of mammalian chromosomes.     

Assignment of the HOX2 and HOX3 gene clusters to the bovine chromosome regions 19q17-qter and 5q14-23

The homeobox 2 (HOX2) and homeobox 3 (HOX3) clusters have been chromosomally assigned in cattle by in situ hybridization. The probes employed were a murine probe for the mapping of HOX2 to 19q17-qter and human probes for the mapping of HOX3 to 5q14-q23. These assignments confirm the chromosomal assignment of two syntenic groups, consisting of loci located on human chromosome 12 (bovine chromosome 5) and the long arm of human chromosome 17 (bovine chromosome 19).     

New gene assignments using a complete, characterized sheep-hamster somatic cell hybrid panel

The generation and characterization of new sheep-hamster cell hybrids is reported from the fusion of sheep white blood cells with six different hamster auxotrophs. Selection from these and previously generated cell hybrids has led to the production of a panel of 30 hybrids covering the complete sheep genome of 28 chromosomes. Over half of the cell hybrids in this panel contain single sheep chromosomes. By complementation, the following new assignments have been made using the panel: phosphoribosyl N-formylglycinamide amidotransferase (PRFGA) to sheep chromosome (chr) 11; adenylosuccinate synthetase (ADSS) to sheep chr 12; adenylosuccinate lyase (ADSL) to sheep chr 3q; 3-hydroxy-3-methylglutaryl-coenzyme A synthase (HMGCS) to sheep chr 16; dihydrofolate reductase (DHFR) to sheep chr 5; and adenine phosphoribosyltransferase (APRT) to sheep chr 14. The gene phosphoribosylaminoinidazole-carboxamide formyltransferase/Inosinicase (PRACFT) has now been regionally assigned to chr 2q. By isozyme analysis, phosphogluconate dehydrogenase (PGD) was assigned to sheep chr 12, anchoring the sheep syntenic group U1 to this chromosome, and mannose phosphate isomerase (MPI) was assigned to sheep chr 18. Furthermore, the chromosomal assignment of 110 microsatellites was confirmed using this cell panel.     

Localization of the ß-subunit of follicle stimulating hormone in cattle and sheep by in situ hybridization

The locus for the beta-subunit of the follicle stimulating hormone gene (FSHB) has been determined in both cattle and sheep by in situ hybridization of a bovine and an ovine cDNA probe, respectively, to metaphase chromosomes. Our results show that the FSHB locus is on cattle chromosome 15 in the region of bands q24-qter and in sheep on the cytogenetically homologous chromosome 15, also in the region q24-qter. The mapping of the FSHB gene in cattle together with the location of other genes (CAT, HBB and PTH) previously found to be syntenic in cattle and on human chromosome 11p, defines an evolutionarily conserved synteny. The localization of the FSHB gene to a cytogenetically homologous region in cattle and sheep is consistent with the hypothesis of extensively conserved chromosome structure in these two species.     

The thyroglobulin gene is syntenic with the MYC and MOS protooncogenes and carbonic anhydrase II and maps to chromosome 14 in cattle

Using a panel of bovine x Chinese hamster hybrid somatic cells, sequences homologous to genes spanning human chromosome arm 8q have been syntenically assigned in cattle. Thyroglobulin (TG), carbonic anhydrase II (CA2), and the protooncogenes MYC and MOS were assigned to a newly identified bovine syntenic group, U23. Additionally, in situ hybridization of the thyroglobulin probe to bovine metaphase chromosomes revealed this syntenic group to be on bovine chromosome 14 and the bovine thyroglobulin gene to reside at 14q12----q15.     

Cytogenetical anchoring of sheep linkage map and syntenic groups using a sheep BAC library

In order to simultaneously integrate linkage and syntenic groups to the ovine chromosomal map, a sheep bacterial artificial chromosome (BAC) library was screened with previously assigned microsatellites using a sheep-hamster hybrid panel and genetic linkage. Thirty-three BACs were obtained, fluorescently labelled and hybridised on sheep-goat hybrid metaphases (2n = 57). This study allowed us, (i), to anchor all linkage groups on sheep chromosomes, (ii), to give information on the probable position of the centromere on the linkage map for the centromeric chromosomes, (iii), to contradict the previous orientation of the ovine × linkage group by the mapping of BMS1008 on OARXq38. Concerning our somatic cell hybrid panel, this study resulted in the assignment of all the previously unassigned groups to ovine chromosomes and a complete characterisation of the hybrid panel. In addition, since hybridisations were performed on a sheep-goat hybrid, new marker/anchoring points were added to the caprine cytogenetic map.     

Six loci mapped on to human chromosome 2p are assigned to sheep chromosome 3p

Six loci, apoliproprotein B (including Ag(x) antigen), immunoglobulin kappa constant region (IGKC), luteinizing hormone/choriogonadotrophin receptor, avian myelocytomatosis viral related oncogene, neuroblastoma derived, ornithine decarboxylase, and proopiomelanocortin (adrenocorticotropin/beta-lipotropin) (POMC), were newly assigned to sheep chromosome 3p using a chromosomally characterized minipanel of sheep-hamster cell hybrids. Isotopic in situ hybridization of IGKC to sheep chromosome 3p22–p17 is reported, confirming the cell hybrid assignment. As these loci are all known to map to human chromosome 2p, this study demonstrates that this chromosomal segment is extensively conserved in sheep. Only POMC has been previously assigned to cattle chromosome 11, which is the equivalent of sheep chromosome 3p. Therefore, we predict that the other loci assigned in this study to sheep 3p are likely to be located on cattle 11. The provisional assignment of an additional locus, annexin-like to sheep chromosome 3p is also reported.     

Comparative mapping of twenty-eight bovine loci in sheep (Ovis aries, 2n = 54) and river buffalo (Bubalus bubalis, 2n = 50) by FISH

Peripheral blood cell cultures were treated for late incorporation of both BrdU and Hoechst-33258 to obtain R-banding pattern preparations. Twenty-eight bovine cosmids from 19 bovine syntenic groups (U), three of which contain type I loci and 25 which contain microsatellite loci and have previously been assigned to cattle chromosomes, were comparatively FISH-mapped to sheep and river buffalo chromosomes according to the standard karyotypes (13 loci for the first time in the latter species). The results enrich the physical maps of both species with information relative to the following loci and to the corresponding syntenic groups: IDVGA35 and IDVGA53 (U6), IDVGA61 and IDVGA84 (U13), JAB10 (U5), IDVGA41 and IDVGA57 (U27), IDVGA87 (U11), IDVGA32 and IDVGA10 (U19), IDVGA49, IDVGA66 and IDVGA68 (U1), ZNF164 (U23), IDVGA74 and IDVGA70 (U9), IDVGA47, IDVGA46 and IDVGA58 (U21), MAP1B (U14), IDVGA79 (U4), CATHL (U12), IDVGA71 (U8), IDVGA59 (U26), IDVGA29 (U29), IDVGA7 (U7), IDVGA82 (X), IDVGA50 (Y). All mapped loci were localized on homoeologous chromosomes and chromosome regions of the two species, confirming the high degree of chromosome homoeologies between the subfamilies Bovinae and Caprinae.     

Comparative gene assignment in Ateles paniscus chamek (Platyrrhini, Primates) and man: association of three separate human syntenic groups and evolutionary considerations

Regional assignment of eight markers to chromosome 2 of Ateles paniscus chamek (APC) confirmed a syntenic association similar to human (HSA) 12q + 14q + 15q. Three HSA 12q markers (RAP1B, PAH and ALDH2) were allocated to a shortest region of overlap (SRO) in APC 2p and found to be syntenic to other HSA 12q markers (PEPB and TCF1). Five HSA 14q markers (CTLA, PAX9, NSP, FOS and CHGA) were allocated to APC 2q and found to be syntenic to other HSA 14q markers (NP, TGM1, and CALM1) and to four HSA 15q markers (THBS1, B2M, HEXA and MPI) but dissociated from markers close to HSA 14qter (CKB) and HSA 15qter (FES-IDH2). Karyotypic comparisons showed an evident homoeology between APC 2p and HSA 12q while APC 2q was similar to an HSA 14qter::HSA 15qter fusion product. Comparative gene mapping data show that the HSA 14q + HSA 15q syntenic association is an ancestral mammalian gene cluster that has been maintained in several primate taxa. Conversely, in Ateles, it has been further associated with HSA 12q while, in Hominoids and Cebus, it has been independently dissociated into two separate syntenic groups, similar to HSA 14q and HSA 15q. Received: 24 October 1997; in revised form: 10 December 1997 / Accepted: 20 December 1997     

Mapping of MYF5, GlR, MYHL, TPIl, IAPP, A2MR and RNR onto sheep chromosome 3q

Five new loci, myogenic factor 5 (MYF5), complement 1 receptor (CIR), myosin-like heavy chain (MYHL), islet amyloid polypeptide (IAPP), and alpha-2-macroglobulin receptor (A2MR), were mapped onto sheep chromosome 3q by Southern hybridization to a panel of chro-mosomally characterized sheep × hamster cell hybrid lines. The location of the triose phosphate isomerase (TPI1) gene and one of the nucleolar organizer regions (RNR) on sheep 3q was confirmed by Southern analysis. This study provides further evidence for the existence of a large conserved chromosomal segment comprising much of sheep chromosome 3q, cattle chromosome 5, and human chromosome 12. The distal evolutionary breakpoint on human chromosome 12, producing the chromosomal segment U23 in cattle marked by aldehyde dehydrogenase (ALDH2), also produces a separate segment in sheep. Neither ALDH2 nor pancreatic lipase (PLA2), which is also distally located on human chromosome 12, were mapped onto sheep chromosome 3q.     

Assignment of five polymorphic ovine microsatellites to bovine syntenic groups

A panel of bovine somatic cell hybrids was used to map ovine microsatellites. Five of seven microsatellites were assigned to five bovine syntenic groups. These microsatellites were designated D5S10 (MAF23), D1S4 (MAF46), D13S1 (MAF18), D4S3 (MAF50), and DXS2 (MAF45), mapped to syntenic groups U3 (chromosome 5), U10 (chromosome 1), U11, U13, and the X chromosome, respectively. Two remaining sheep microsatellites amplified rodent DNA in the hybrid somatic cell panel, and were not assigned to bovine syntenic groups. Assignment of ovine-derived microsatellites to bovine syntenic groups provides additional evidence of the usefulness of microsatellites for mapping closely related species. The use of ovine and bovine microsatellites will aid in development of comparative genomic maps for these two species.     

Genomic analysis of the major bovine milk protein genes.

The genomic arrangement of the major bovine milk protein genes has been determined using a combination of physical mapping techniques. The major milk proteins consist of the four caseins, alpha s1 (CASAS1), alpha s2 (CASAS2), beta (CASB), and kappa (CASK), as well as the two major whey proteins, alpha-lactalbumin (LALBA) and beta-lactoglobulin (LGB). A panel of bovine X hamster hybrid somatic cells analyzed for the presence or absence of bovine specific restriction fragments revealed the genes coding for the major milk proteins to reside on three chromosomes. The four caseins were assigned to syntenic group U15 and localized to bovine chromosome 6 at q31-33 by in situ hybridization. LALBA segregated with syntenic group U3, while LGB segregated with U16. Pulsed-field gel electrophoresis confirmed genetic mapping results indicating tight linkage of the casein genes. The four genes reside on less than 200 kb of DNA in the order CASAS1-CASB-CASAS2-CASK. Multiple restriction fragment length polymorphisms were also found at the six loci in three breeds of cattle.     

Conserved autosomal syntenic group on mouse (MMU) chromosome 15 and human (HSA) chromosome 22: assignment of a gene for arylsulfatase A to MMU 15 and regional mapping of DIA1, ARSA, and ACO2 on HSA 22

We have utilized a panel of Chinese hamster x mouse somatic cell hybrids segregating mouse chromosomes to assign a gene for arylsulfatase A (ARSA) to mouse chromosome 15. Considering our previous assignment of a gene for diaphorase-1 (DIA1) to the same mouse chromosome, we have evidence for another syntenic relationship that has been conserved, since the homologous loci for human ARSA and DIA1 are both located on human chromosome 22. Because MMU 15 and HSA 22 are quite dissimilar in size and banding patterns, we have attempted to identify the conserved portion by regional mapping of human DIA1 and ARSA using somatic cell hybrids segregating a human chromosome translocation t(15;22)(q14;q13.31). The results assign human DIA1 and ARSA to the distal sub-band of 22q13 (region 22q13.31 leads to qter). The locus for mitochondrial aconitase (ACO2) has been separated by the breakpoint from DIA1 and ARSA and is located more proximally.     

Chromosome banding and gene localizations support extensive conservation of chromosome structure between cattle and sheep.

By using three gene probes, one derived from the porcine major histocompatibility complex (MHC) and two from bovine cytokeratin genes, type I (KRTA) and type II (KRTB), the hypothesis of conservation of genome structure in two members of the family Bovidae was examined. Gene mapping data revealed the MHC to be in chromosome region 23q15----q23 in cattle (BOLA) and 20q15----q23 in sheep (OLA). KRTA was localized to chromosome region 19q25----q29 in cattle and 11q25----q29 in sheep and KRTB to 5q14----q22 in cattle and 3q14----q22 in sheep. The banding patterns of the chromosome arms to which the loci were assigned were identical in both species. Moreover, the resemblances of GTG- or QFQ-banding patterns between the cattle and sheep karyotypes illustrated further chromosome homologies. These studies, based on gene mapping comparisons and comparative cytogenetics, document that within bovid chromosomes, homology of banding patterns corresponds to a homologous genetic structure. Hence, we propose that gene assignments on identified chromosomal segments in one species of the Bovidae can be extrapolated, in general, to other bovid species based on the banding homologies presented here.     

Chromosome localization of the 31 type I Texas bovine markers in sheep and goat chromosomes by comparative FISH-mapping and R-banding

Bovine BAC clones containing the 31 genes, referred to as the Texas markers used earlier to definitively assign the 31 bovine syntenic groups (U) to cattle chromosomes, were mapped by fluorescent in situ hybridization to sheep and goat R-banded chromosomes according to ISCNDB2000. All 31 markers were localized on homoeologous chromosomes and chromosome bands of the two species in agreement with previous localizations obtained both in cattle and river buffalo, definitively confirming chromosome homoeologies between Caprinae and Bovinae. In addition, we have extended physical maps of sheep and goat as 11 genes (HSD3B1, INHBA, CSN10, IGF2R, PIGR, MAP1B, DSC1, ELN, TNFRSF6, CGN1, IGF2) and 14 genes (SOD1, HSD3B1, CSN10, IGF2R, RB1, TG, PIGR, MAP1B, IGH@, LTF, DSC1, TNFRSF6, CGN1, IGF2) were assigned for the first time to goat and sheep chromosomes, respectively.     

A Genetic Linkage Map for Cattle

We report the most extensive physically anchored linkage map for cattle produced to date. Three-hundred thirteen genetic markers ordered in 30 linkage groups, anchored to 24 autosomal chromosomes (n = 29), the X and Y chromosomes, four unanchored syntenic groups and two unassigned linkage groups spanning 2464 cM of the bovine genome are summarized. The map also assigns 19 type I loci to specific chromosomes and/or syntenic groups and four cosmid clones containing informative microsatellites to chromosomes 13, 25 and 29 anchoring syntenic groups U11, U7 and U8, respectively. This map provides the skeletal framework prerequisite to development of a comprehensive genetic map for cattle and analysis of economic trait loci (ETL).