Examination of FGFRL1 as a candidate gene for diaphragmatic defects at chromosome 4p16.3 shows that Fgfrl1 null mice have reduced expression of Tpm3, sarcomere genes and Lrtm1 in the diaphragm

Fgfrl1 (also known as Fgfr5; OMIM 605830) homozygous null mice have thin, amuscular diaphragms and die at birth because of diaphragm hypoplasia. FGFRL1 is located at 4p16.3, and this chromosome region can be deleted in patients with congenital diaphragmatic hernia (CDH). We examined FGFRL1 as a candidate gene for the diaphragmatic defects associated with 4p16.3 deletions and re-sequenced this gene in 54 patients with CDH. We confirmed six known coding single nucleotide polymorphisms (SNPs): c.209G > A (p.Pro20Pro), c.977G > A (p.Pro276Pro), c.1040T > C (p.Asp297Asp), c.1234C > A (p.Pro362Gln), c.1420G > T (p.Arg424Leu), and c.1540C > T (p.Pro464Leu), but we did not identify any gene mutations. We genotyped additional CDH patients for four of these six SNPs, including the three non-synonymous SNPs, to make a total of 200 chromosomes, and found that the allele frequency for the four SNPs, did not differ significantly between patients and normal controls (p > or = 0.05). We then used Affymetrix Genechip Mouse Gene 1.0 ST arrays and found eight genes with significantly reduced expression levels in the diaphragms of Fgfrl1 homozygous null mice when compared with wildtype mice-Tpm3, Fgfrl1 (p = 0.004), Myl2, Lrtm1, Myh4, Myl3, Myh7 and Hephl1. Lrtm1 is closely related to Slit3, a protein associated with herniation of the central tendon of the diaphragm in mice. The Slit proteins are known to regulate axon branching and cell migration, and inhibition of Slit3 reduces cell motility and decreases the expression of Rac and Cdc42, two genes that are essential for myoblast fusion. Further studies to determine if Lrtm1 has a similar function to Slit3 and if reduced Fgfrl1 expression can cause diaphragm hypoplasia through a mechanism involving decreased myoblast motility and/or myoblast fusion, seem indicated.

Mapping of a new locus for congenital anomalies of the kidney and urinary tract on chromosome 8q24

Congenital anomalies of the kidney and urinary tract (CAKUT) account for the majority of end-stage renal disease in children (50%). Previous studies have mapped autosomal dominant loci for CAKUT. We here report a genome-wide search for linkage in a large pedigree of Somalian descent containing eight affected individuals with a non-syndromic form of CAKUT.

Bipolar disorder susceptibility region on chromosome 3q29 not confirmed in a case-control association study

We identified a bipolar disorder (BPD) susceptibility region on chromosome 3q29 in a genome-wide linkage scan (Bailer et al. 2002 (Biol Psychiatry 52: 40), NPL-score 4.09) and follow-up linkage analysis (Schosser et al. 2004 (J Psychiatr Res 38(3): 357), NPL-scores >3 with five markers). These findings were supported by further fine-mapping of this region (Schosser et al. 2007 (Eur Neuropsychopharmacol 17(6-7): 501)), finding NPL-scores >3.9 with SNPs (single nucleotide polymorphisms) spanning a region of 3.46 Mbp in BPD families. Since genetic association studies are more powerful than linkage studies for detecting susceptibility genes of small effect size, we aimed to replicate these findings in an independent case-control sample collected in London (UK) and Vienna (Austria).

A locus on chromosome 5 is associated with dilated cardiomyopathy in Doberman Pinschers

Dilated cardiomyopathy (DCM) is a heterogeneous group of heart diseases with a strong genetic background. Currently, many human DCM cases exist where no causative mutation can be identified. DCM also occurs with high prevalence in several large dog breeds. In the Doberman Pinscher a specific DCM form characterized by arrhythmias and/or echocardiographic changes has been intensively studied by veterinary cardiologists. We performed a genome-wide association study in Doberman Pinschers. Using 71 cases and 70 controls collected in Germany we identified a genome-wide significant association to DCM on chromosome 5. We validated the association in an independent cohort collected in the United Kingdom. There is no known DCM candidate gene under the association signal. Therefore, DCM in Doberman Pinschers offers the chance of identifying a novel DCM gene that might also be relevant for human health.

Gain of chromosome 8q is associated with metastases and poor survival of patients with clear cell renal cell carcinoma

The aim of this study was to evaluate the prevalence of chromosome 8q gain in clear cell renal cell carcinoma (CCRCC) and to correlate the findings with tumor phenotype and disease-specific survival (DSS).

A high-resolution comparative radiation hybrid map of equine chromosome 4q12-q22

In this study, we present a comprehensive 5000-rad radiation hybrid map of a 40-cM region on equine chromosome 4 (ECA4) that contains quantitative trait loci for equine osteochondrosis. We mapped 29 gene-associated sequence tagged site markers using primers designed from equine expressed sequence tags or BAC clones in the ECA4q12-q22 region. Three blocks of conserved synteny, showing two chromosomal breakpoints, were identified in the segment of ECA4q12-q22. Markers from other segments of HSA7q mapped to ECA13p and ECA4p, and a region of HSA7p was homologous to ECA13p. Therefore, we have improved the resolution of the human-equine comparative map, which allows the identification of candidate genes underlying traits of interest.

Single linkage group per chromosome genetic linkage map for the horse, based on two three-generation, full-sibling, crossbred horse reference families

A genetic linkage map of the horse consisting of 742 markers, which comprises a single linkage group for each of the autosomes and the X chromosome, is presented. The map has been generated from two three-generation full-sibling reference families, sired by the same stallion, in which there are 61 individuals in the F2 generation. Each linkage group has been assigned to a chromosome and oriented with reference to markers mapped by fluorescence in situ hybridization. The average interval between markers is 3.7 cM and the linkage groups collectively span 2772 cM. The 742 markers comprise 734 microsatellite and 8 gene-based markers. The utility of the microsatellite markers for comparative mapping has been significantly enhanced by comparing their flanking sequences with the human genome sequence; this enabled conserved segments between human and horse to be identified. The new map provides a valuable resource for genetically mapping traits of interest in the horse.

Molecular characterization of the equine collagen, type IX, alpha 2 (COL9A2) gene on horse chromosome 2p16-->p15

The mammalian collagen, type IX, alpha 2 gene (COL9A2) encodes the alpha-2 chain of type IX collagen and is located on horse chromosome 2p16-->p14 harbouring a quantitative trait locus for osteochondrosis. We isolated a bacterial artificial chromosome (BAC) clone containing the equine COL9A2 gene and determined the complete genomic sequence of this gene. Cloning and characterization of equine COL9A2 revealed that the equine gene consists of 32 exons spanning approximately 15 kb. The COL9A2 transcript encodes a single protein of 688 amino acids. Thirty two single nucleotide polymorphisms (SNPs) equally distributed in the gene were detected in a mutation scan of eight unrelated Hanoverian warmblood stallions, including one SNP that affects the amino acid sequence of COL9A2. Comparative analyses between horse, human, mouse and rat indicate that the chromosomal location of equine COL9A2 is in agreement with known chromosomal synteny relationships. The comparison of the gene structure and transcript revealed a high degree of conservation towards the other mammalian COL9A2 genes. We chose three informative SNPs for association and linkage disequilibrium tests in three to five paternal half-sib families of Hanoverian warmblood horses consisting of 44 to 75 genotyped animals. The test statistics did not reach the significance threshold of 5% and so we could not show an association of COL9A2 with equine osteochondrosis.

Age at diagnosis and loss of heterozygosity on chromosome 1p and 19q in oligodendroglial tumors

The age distribution and incidence of loss of heterozygosity (LOH) of 1p and 19q was analyzed in 85 oligodendroglial tumors WHO II and III. The peak of tumor manifestation was in the age group of 35 to 55 years. There was no association between age at diagnosis and LOH incidence. We conclude that the prognostic effect of age on survival is not mediated by LOH 1p/19q.

Linkage mapping of ovine microphthalmia to chromosome 23, the sheep orthologue of human chromosome 18

PURPOSE: To characterize the phenotype and map the locus responsible for autosomal recessive inherited ovine microphthalmia (OMO) in sheep. METHODS: Microphthalmia-affected lambs and their available relatives were collected in a field, and experimental matings were performed to obtain affected and normal lambs for detailed necropsy and histologic examinations. The matings resulted in 18 sheep families with 48 cases of microphthalmia. A comparative candidate gene approach was used to map the disease locus within the sheep genome. Initially, 27 loci responsible for the microphthalmia-anophthalmia phenotypes in humans or mice were selected to test for comparative linkage. Fifty flanking markers that were predicted from comparative genomic analysis to be closely linked to these genes were tested for linkage to the disease locus. After observation of statistical evidence for linkage, a confirmatory fine mapping strategy was applied by further genotyping of 43 microsatellites. RESULTS: The clinical and pathologic examinations showed slightly variable expressivity of isolated bilateral microphthalmia. The anterior eye chamber was small or absent, and a white mass admixed with cystic spaces extended from the papilla to the anterior eye chamber, while no recognizable vitreous body or lens was found within the affected eyes. Significant linkage to a single candidate region was identified at sheep chromosome 23. Fine mapping and haplotype analysis assigned the candidate region to a critical interval of 12.4 cM. This ovine chromosome segment encompasses an ancestral chromosomal breakpoint corresponding to two orthologue segments of human chromosomes 18, short and long arms. For the examined animals, we excluded the complete coding region and adjacent intronic regions of ovine TGIF1 to harbor disease-causing mutations. CONCLUSIONS: This is the first genetic localization for hereditary ovine isolated microphthalmia. It seems unlikely that a mutation in the TGIF1 gene is responsible for this disorder. The studied sheep represent a valuable large animal model for similar human ocular phenotypes.

A radiation hybrid map of sheep chromosome 23 based on ovine BAC-end sequences

More than 375,000 BAC-end sequences (BES) of the CHORI-243 ovine BAC library have been deposited in public databases. blastn searches with these BES against HSA18 revealed 1806 unique and significant hits. We used blastn-anchored BES for an in silico prediction of gene content and chromosome assignment of comparatively mapped ovine BAC clones. Ovine BES were selected at approximately 1.3-Mb intervals of HSA18 and incorporated into a human-sheep comparative map. An ovine 5000-rad whole-genome radiation hybrid panel (USUoRH5000) was typed with 70 markers, all of which mapped to OAR23. The resulting OAR23 RH map included 43 markers derived from BES with high and unique BLAST hits to the sequence of the orthologous HSA18, nine EST-derived markers, 16 microsatellite markers taken from the ovine linkage map and two bovine microsatellite markers. Six new microsatellite markers derived from the 43 mapped BES and the two bovine microsatellite markers were linkage-mapped using the International Mapping Flock (IMF). Thirteen additional microsatellite markers were derived from other ovine BES with high and unique BLAST hits to the sequence of the orthologous HSA18 and also positioned on the ovine linkage map but not incorporated into the OAR23 RH map. This resulted in 24 markers in common and in the same order between the RH and linkage maps. Eight of the BES-derived markers were mapped using fluorescent in situ hybridization (FISH), to thereby align the RH and cytogenetic maps. Comparison of the ovine chromosome 23 RH map with the HSA18 map identified and localized three major breakpoints between HSA18 and OAR23. The positions of these breakpoints were equivalent to those previously shown for syntenic BTA24 and HSA18. This study presents evidence for the usefulness of ovine BES when constructing a high-resolution comprehensive map for a single sheep chromosome. The comparative analysis confirms and refines knowledge about chromosomal conservation and rearrangements between sheep, cattle and human. The constructed RH map demonstrates the resolution and utility of the newly constructed ovine RH panel.

The locus for bovine dilated cardiomyopathy maps to chromosome 18

Bovine dilated cardiomyopathy (BDCMP) is a severe and terminal disease of the heart muscle observed in Holstein-Friesian cattle over the last 30 years. There is strong evidence for an autosomal recessive mode of inheritance for BDCMP. The objective of this study was to genetically map BDCMP, with the ultimate goal of identifying the causative mutation. A whole-genome scan using 199 microsatellite markers and one SNP revealed an assignment of BDCMP to BTA18. Fine-mapping on BTA18 refined the candidate region to the MSBDCMP06-BMS2785 interval. The interval containing the BDCMP locus was confirmed by multipoint linkage analysis using the software loki. The interval is about 6.7 Mb on the bovine genome sequence (Btau 3.1). The corresponding region of HSA19 is very gene-rich and contains roughly 200 genes. Although telomeric of the marker interval, TNNI3 is a possible positional and a functional candidate for BDCMP given its involvement in a human form of dilated cardiomyopathy. Sequence analysis of TNNI3 in cattle revealed no mutation in the coding sequence, but there was a G-to-A transition in intron 6 (AJ842179:c.378+315G>A). The analysis of this SNP using the study's BDCMP pedigree did not conclusively exclude TNNI3 as a candidate gene for BDCMP. Considering the high density of genes on the homologous region of HSA19, further refinement of the interval on BTA18 containing the BDCMP locus is needed.