Missense mutations and polymorphisms of the MC4R gene in Polish obese children and adolescents in relation to the relative body mass index

Extensive studies of the MC4R gene polymorphism showed that, among numerous variants, there are mutations responsible for monogenic obesity, as well as polymorphisms negatively correlated with the risk of obesity. In this report, we present the first studies of the whole coding sequence of the MC4R gene in 243 Polish obese children and adolescents (the mean relative body mass index [RBMI] was 163.6). In addition, 101 non-obese adults were also analyzed. Direct sequencing facilitated the identification of six missense (K73R, V103I, T112M, S127L, M215L, and I251L) and one silent (c.756 C > T) single-nucleotide polymorphisms (SNPs). Two non-synonymous polymorphisms (K73R and M215L) appeared to be novel and one was found in obese patients (M215L, one patient) and one in non-obese adults (K73R, one person). The overall frequency of non-synonymous variant carriers reached 4.1% and 6.9% in obese patients and non-obese adults, respectively. Only one obesity-associated variant (127L) was found in two obese patients (0.82%) and in two non-obese adults (1.98%). The obesity-protecting variants (103I and 251L) appeared to be the most common in both groups: 3.3% and 4.0%, respectively. It was also observed that the RBMI in obese children and adolescents carrying the minor variants did not differ significantly from the non-carriers; however, the expected trends for the associated and protecting variants were observed. We conclude that the contribution of the MC4R gene variants to the pathogenesis of obesity in Polish children and adolescents is low.

A novel mutation in the maternally imprinted PEG3 domain results in a loss of MIMT1 expression and causes abortions and stillbirths in cattle (Bos taurus)

Congenital malformations resulting in late abortions and stillbirths affect the economic wellbeing of producers and the welfare of cattle in breeding programs. An extremely high incidence of stillbirths of “half-sized” calves of normal karyotype and uninflated lungs was diagnosed in the progeny of the Finnish Ayrshire (Bos taurus) bull - YN51. No other visible anatomical abnormalities were apparent in the stillborn calves. We herein describe the positional identification of a 110 kb microdeletion in the maternally imprinted PEG3 domain that results in a loss of paternal MIMT1 expression and causes late term abortion and stillbirth in cattle. Using the BovineSNP50 BeadChip we performed a genome-wide half-sib linkage analysis that identified a 13.3 Mb associated region on BTA18 containing the maternally imprinted PEG3 domain. Within this cluster we found a 110 kb microdeletion that removes a part of the non-protein coding MER1 repeat containing imprinted transcript 1 gene (MIMT1). To confirm the elimination of gene expression in calves inheriting this deletion, we examined the mRNA levels of the three maternally imprinted genes within the PEG3 domain, in brain and cotyledon tissue collected from eight fetuses sired by the proband. None of the fetuses that inherited the microdeletion expressed MIMT1 in either tissue. The mutation, when inherited from the sire, is semi-lethal for his progeny with an observed mortality rate of 85%. The survival of 15% is presumably due to the incomplete silencing of maternally inherited MIMT1 alleles. We designed a PCR-based assay to confirm the existence of the microdeletion in the MIMT1 region that can be used to assist cattle breeders in preventing the stillbirths.

A case of Y-autosome reciprocal translocation in a Holstein-Friesian bull

Cytogenetic evaluation of young bulls of the Polish Holstein-Friesian breed, tested before approving for use in artificial insemination, revealed a carrier of a Y-autosome reciprocal translocation. The applied chromosome banding techniques and fluorescence in situ hybridization (FISH), with the use of locus-specific BAC probes, facilitated description of the translocation as t(Y;21)(p11;q11). The bull presented normal development, including body weight and the size of testicles, as well as libido. Testosterone concentration at the age of 8 months was similar in the carrier and a normal bull of the same age, but at the age of 12 months the testosterone concentration appeared to be lower in the carrier.

A comparison of coding sequence and cytogenetic localization of the myostatin gene in the dog, red fox, arctic fox and Chinese raccoon dog

The gene encoding myostatin (MSTN), due to its crucial function for growth of skeletal muscle mass, is an important candidate for muscularity. In this study we analyzed the nucleotide sequence and FISH localization of this gene in 4 canids, including 3 farm species. The nucleotide sequence of the MSTN coding fragment turned out to be highly conserved, since its identity among the studied species was very high and varied between 99.4 and 99.7%. Only 1, widely spread, silent single nucleotide polymorphism (SNP) was found in exon 1 of the Chinese raccoon dog. The MSTN gene was localized close to the centromere in one-armed chromosomes of the dog (37q11) and bi-armed chromosomes of the red fox (16p11) and arctic fox (10q11), with an exception of the Chinese raccoon dog chromosome (2q14-q21). This chromosome is orthologous to 3 canine chromosomes and thus the MSTN was found more interstitially. Our results are in agreement with the hypothesis that karyotypes of the canids evolved mainly through centric fusion/fission events, while tandem fusions occurred rarely.

Variability of CAG tandem repeats in exon 1 of the androgen receptor gene is not related with dog intersexuality

Numerous mutations of the human androgen receptor (AR) gene cause an intersexual phenotype, called the androgen insensitivity syndrome. The intersexual phenotype is also quite often diagnosed in dogs. The aim of this study was to conduct a comparative analysis of the entire coding sequence (eight exons) of the AR gene in healthy and four intersex dogs, as well as in three other canids (the red fox, arctic fox and Chinese raccoon dog). The coding sequence of the studied species appeared to be conserved (similarity above 97%) and polymorphism was found in exon 1 only. Altogether, 2 SNPs were identified in healthy dogs, 14 in red foxes, 16 in arctic foxes and 6 were found in Chinese raccoon dogs, respectively. Moreover, a variable number of tandem repeats (CAG and CAA), encoding an array of glutamines, was also observed in this exon. The CAA codon numbers were invariable within species, but the CAG repeats were polymorphic. The highest number of the CAG and CAA repeats was found in dogs (from 40 to 42) and the observed variability was similar in intersex and healthy dogs. In the other canids the variability fell within the following ranges: 29-37 (red fox), 37-39 (arctic fox) and 29-32 (Chinese raccoon dog). In addition, a polymorphic microsatellite marker in intron 2 was found in the dog, red fox and Chinese raccoon dog. It was concluded that the polymorphism level of the AR gene in the dog was lower than in the other canids and none of the detected polymorphisms, including variability of the CAG tandem repeats, could be related with the intersexual phenotype of the studied dogs.

Chromosomal localization of 13 candidate genes for human obesity in the pig genome

Thirteen candidate genes for human obesity were selected for cytogenetic mapping by FISH in the pig genome. Among them, 6 genes were assigned to chromosomes for the first time (NR3C1, GNB3, ADRB1, ADRB2, ADRB3 and UCP1). Location of the other 7 genes (INSIG2, LIPIN1, PLIN, NAMPT, ADIPOQ, UCP2 and UCP3), earlier mapped by somatic cell hybridization or with the use of a radiation hybrid panel, was verified (INSIG2) or more precisely described. The genes were assigned to the following chromosomes: INSIG2 to SSC15q12, LIPIN1 to SSC3q26, NR3C1 to SSC2q29, PLIN to SSC7q15, GNB3 to SSC5q21, NAMPT to SSC9q23, ADIPOQ to SSC13q41, ADRB1 to SSC14q28, ADRB2 to SSC2q29, ADRB3 to SSC15q13-14, UCP1 to SSC8q21-22, and both UCP2 and UCP3 to SSC9p24. Most of the genes were located within known QTL for pig fatness traits.

Identification of a new reciprocal translocation in an AI bull by synaptonemal complex analysis, followed by chromosome painting

An AI Ayrshire bull was subjected to cytogenetic examination due to lowered fertility. Preliminary Giemsa staining revealed a normal chromosome complement (60,XY) and G-banding did not allow us to draw a clear conclusion concerning an occurrence of chromosome rearrangement. Testicles were collected at slaughter and synaptonemal complex (SC) analysis revealed a large cross-shaped tetravalent configuration in pachytene spreads. No association between the tetravalent and XY bivalent was observed. Chromosome painting, with the use of bovine whole chromosome painting probes, conjugated with DAPI staining, facilitated a detailed description of the translocation rcp(2;4)(q45;q34). This study shows that post mortem analysis of synaptonemal complexes is a simple and useful tool for the preliminary detection of reciprocal translocation carriers.

Cytogenetic mapping and STR polymorphism of two candidate genes (<i>DRD2</i> and <i>HTR1D</i>) for behaviour traits in four canids (short communication)

Abstract. The dopamine D2 receptor (DRD2) and serotonin receptors 1D (HTR1D) are candidate genes for behavioural traits. In the present study, we show chromosomal location and polymorphism of these genes in four species from the family Canidae: dog (CFA), red fox (VVU), arctic fox (ALA) and the Chinese raccoon dog (NPP). Using fluorescence in situ hybridisation (FISH) the DRD2 gene was localized in the following chromosomes: CFA5q12-13, VVU12q21, ALA10q14 and NPP3q14 and the HTR1D gene was mapped to: CFA2q25, VVU2q22, ALA8q25 and NPP10q25. A microsatellite marker (TG)n in intron 3 of the DRD2 gene and (CA)n motif located in a 3’-flanking region of the HTR1D gene were polymorphic in all studied species. The obtained results can be helpful in further studies on effects of polymorphisms of these genes on behaviour traits in canids.

Normal male chromosome complement and a lack of the SRY and SOX9 gene mutations in a male pseudohermaphrodite dog

In this report we present a case of the male-to-female sex reversal syndrome in a Dachshund bitch. The animal was subjected for examination due to the enlargement of clitoris and male-type behaviour. The cytogenetic analysis (Giemsa staining and FISH with sex chromosome specific probes) revealed a normal male chromosome complement (78,XY). The molecular analysis of the SRY and SOX9 genes with the use of SSCP technique did not reveal any polymorphism. Blood testosterone concentration was low (0.75 ng/ml), thus the androgen insensitivity syndrome could be excluded. We suggest that this case may represent a persistent Müllerian duct syndrome.