Cattle Genome Mapping - Current Scenario - Part 3

However, just as some major drawbacks about the cloning effort are beginning to make this biological idea begin to feel quite impractical, so too perhaps would emerge one by one, the impractical applications of pinpointing malfunctioning genes for therapeutic targets.

In this article and the continuing part of this article, some developments, implications, observations and results of different studies related to the bovine genome will be highlighted. While the implications of some develeopments may make the general public wake up to facts that look like they have been generated in a horror movie, the truth has to be known. The newer a technology and the more incomprehensible it appears, the more sinister it looks. Demystifying ideas can highlight both the drawbacks and the advantages. It remains for humankind to make a wise choice. Even as pharamaceutical companies and breeding associations play cheerleaders, activists concerned about the ethical issues involved work as whistle blowers.

Roslin Institute
At the Roslin Institute, in Scotland, Edinburgh, a flurry of genome mapping projects in both companion animals and domestic animals has been racing ahead. Several genome maps have neared different stages of completion. The institute serves as a centrepoint in coordinating research activity with major genome mapping centres in Europe and US. Databases of several domestic species of animals and birds are freely available at the website- www.thearkdb.org.

Cattle-human whole genome comparative map
Band et al at the University of Illinois at Urbana-Champaign have worked on constructing a cattle-human whole-genome comparative map. The map includes 92% of all cattle chromosomal DNA. The investigators have created parallel radiation hybrid (RH) mapping in conjunction with EST sequencing and database mining for unmapped cattle genes. The researchers found the COMPASS in silico mapping tool to be 95% accurate in its ability to predict cattle chromosome location from random sequence data, demonstrating this tool to be valuable for efficient targeting of specific regions for detailed mapping.

BAC Library
Eggen et al at the Laboratory of Cytogenetics, Cedex, France have developed a bovine artificial chromosome (BAC) library of 105 984 clones in the vector pBeloBAC11. The BAC library extends the international genome coverage for cattle to around 28 genome equivalents. In other studies as that carried out by Buitkamp et al at the University of Munchen in Germany, a (BAC) library has been developed from leukocytes of a Holstein-Friesian male.

QTL and DNA chips
If a genetic marker and a (trait) gene are very close, there is a tendency for associations between specific marker and trait gene alleles to be maintained at a population level. The most abundant class of genetic variation and hence potential markers are single nucleotide polymorphisms (SNPs), i.e. where two DNA sequences differ by a single base (letter).

As most of these traits are quantitative in nature with animals exhibiting a range of phenotypes the regions of the genome which contain these genes are known as Quantitative Trait Loci (or QTL). Recent technical developments however, have created the opportunities to study the expression of thousands of genes simultaneously e.g using DNA chips or microarrays.

Twinning gene identified
Kirkpatrick et al at the University of Wisconsin Madison have identified a single gene on chromosome 19 that affects ovulation rate. Besides this, the team has also identified other genes on chromosome 5 and 7 that act in a similar manner.

The researchers have developed a new DNA test that can clearly pinpoint the form of chromosome 19 linked with high ovulation rate. The new test can help breeders to identify and buy cattle which test positive for this gene, implying that the chances of those cows conceiving twins is significantly higher.

In other studies as that carried out by Lien et al at the Agricultural University of Norway, an autosomal genome scan for quantitative trait loci (QTL) affecting twinning rate was carried out in the Norwegian Cattle population. The investigators found QTL that needed more careful scrutinization on Chromosomes (Chr) 5, 7, 12, and 23.

CIN and Chromosome 1
Kobayashi et al in Japan have identified the locus responsible for chronic interstitial nephritis in cattle to chromosome 1. The condition which is characterized by diffuse zonal fibrosis (CINF) occurs in Japanese Black cattle (Wagyu). It has been identified as an autosomal recessive disorder that causes death prior to puberty, in the first six months or a year of life. The investigators found that the CINF locus to bovine chromosome 1.mapped closest to microsatellites BM9019 and INRA49 (Z score = 12.0; P < 3.4 x 10(-10)).

NRAMP, sst and susceptibility to TB
In clinical investigations of cattle affected with tuberculosis, Barthel et al at the College of Veterinary Medicine, Texas A&M University have observed that the NRAMP1 gene has no role to play in determining resistance and susceptibility to infection with M bovis.

Kramnik et al at the Harvard School of Public Health have identified a new locus with a major effect on tuberculosis susceptibility, called sst1 (susceptibility to tuberculosis 1). The locus has been mapped to a 9-centimorgan (cM) interval on mouse chromosome 1. It is located 10-19 cM distal to Nramp1. According to the researchers, sst1 controls progression of tuberculosis infection in a lung-specific manner.

QTL, mastits and somatic cell count
Klungland et al at the Agricultural University of Norway have localized significant QTL affecting clinical mastitis to bovine Chromosome (Chr) 6. Besides that, additional QTL for clinical mastitis were localized to Chrs. 3, 4, 14, and 27.

BCNT gene
Iwashita et al at the Mitsubishi Kasei Institute of Life Sciences have successfully mapped the BCNT ( Bucentaur or craniofacial development protein 1) gene to chromosome 18. Bovine BCNT contains a region of the endonuclease domain derived from a truncated RTE-1 (previously called Bov-B LINE), a non-LTR retrotransposable repetitive element, and two repeat units (intramolecular repeat, IR) each with 40 amino acids in the C-terminal region.

Bovine Chromosome 18
Goldammer et al at the Texas A & M University have constructed a comprehensive radiation hybrid (RH) map and a high resolution comparative map of Bos taurus (BTA) chromosome 18. The map made up of 103 markers and 76 markers, respectively, used a cattle-hamster somatic hybrid cell panel and a 5,000 rad whole-genome radiation hybrid (WGRH) panel. The ivestigators have reported that there was a conserved synteny between cattle, human, and mouse for 76 genes of BTA18 and human chromosomes (HSA) 16 and 19 and for 34 cattle genes and mouse chromosomes (MMU) 7 and 8.

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