A nonsense mutation in CEP55 defines a new locus for a Meckel-like syndrome, an autosomal recessive lethal fetal ciliopathy.

Mutations in genes involved in the cilium-centrosome complex are called ciliopathies. Meckel-Gruber syndrome (MKS) is a ciliopathic lethal autosomal recessive syndrome characterized by genetically and clinically heterogeneous manifestations, including renal cystic dysplasia, occipital encephalocele and polydactyly. Several genes have previously been associated with MKS and MKS-like phenotypes, but there are still genes remaining to be discovered. We have used whole-exome sequencing (WES) to uncover the genetics of a suspected autosomal recessive Meckel syndrome phenotype in a family with 2 affected fetuses. RNA studies and histopathological analysis was performed for further delineation. WES lead to identification of a homozygous nonsense mutation c.256C>T (p.Arg86*) in CEP55 (centrosomal protein of 55 kDa) in the affected fetus. The variant has previously been identified in carriers in low frequencies, and segregated in the family. CEP55 is an important centrosomal protein required for the mid-body formation at cytokinesis. Our results expand the list of centrosomal proteins implicated in human ciliopathies and provide evidence for an essential role of CEP55 during embryogenesis and development of disease.

Microphthalmia-associated transcription factor mutations are associated with white-spotted coat color in swamp buffalo.

A candidate gene analysis of the microphthalmia-associated transcription factor (MITF) gene was used in an attempt to identify the genetic basis for a white-spotted coat color phenotype in the Asian swamp buffalo (Bubalus bubalis carabanensis). Ninety-three buffaloes-32 solid, 38 spotted and 23 white individuals-were Sanger-sequenced for all MITF exons as well as highly conserved intronic and flanking regions. MITF cDNA representing skin and iris tissue from six spotted, nine solid and one white buffaloes was also Sanger-sequenced to confirm detected mutations. Two independent loss-of-function mutations, a premature stop codon (c.328C>T, p.Arg110*) and a donor splice-site mutation (c.840+2T>A, p.Glu281_Leu282Ins8), both of which cause white-spotted coat color in swamp buffaloes, were identified. The nonsense mutation leads to a premature stop codon in exon 3, and likely removal of the resulting mRNA via nonsense-mediated decay pathway, whereas the donor splice-site mutation leads to aberrant splicing of exon 8 that encodes part of a highly conserved region of MITF. The resulting insertion of eight amino acid residues is expected to perturb the leucine zipper part in the basic helix-loop-helix leucine zipper (bHLH-Zip) domain and will most likely influence dimerization and DNA binding capacity. Electrophoretic mobility shift assay was performed using mutant and wild-type MITF proteins and showed that the mutant MITF protein resulting from the splice-site mutation decreased in vitro DNA binding capacity compared to wild-type MITF. White-spotted buffalo bulls are sacrificed in funeral ceremonies in Tana Toraja, Indonesia, because they are considered holy, and our results show that genetic variation causes a tie to the cultural use of these buffaloes.

MHC class II is an important genetic risk factor for canine systemic lupus erythematosus (SLE)-related disease: implications for reproductive success.

Major histocompatibility complex (MHC) class II genes are important genetic risk factors for development of immune-mediated diseases in mammals. Recently, the dog (Canis lupus familiaris) has emerged as a useful model organism to identify critical MHC class II genotypes that contribute to development of these diseases. Therefore, a study aimed to evaluate a potential genetic association between the dog leukocyte antigen (DLA) class II region and an immune-mediated disease complex in dogs of the Nova Scotia duck tolling retriever breed was performed. We show that DLA is one of several genetic risk factors for this disease complex and that homozygosity of the risk haplotype is disadvantageous. Importantly, the disease is complex and has many genetic risk factors and therefore we cannot provide recommendations for breeders exclusively on the basis of genetic testing for DLA class II genotype.

Increased genetic risk or protection for canine autoimmune lymphocytic thyroiditis in Giant Schnauzers depends on DLA class II genotype.

Dogs represent an excellent comparative model for autoimmune thyroiditis as several dog breeds develop canine lymphocytic thyroiditis (CLT), which is clinically similar to Hashimoto's thyroiditis in human. We obtained evidence that dog leukocyte antigen (DLA) class II genotype function as either genetic risk factor that predisposes for CLT or as protective factor against the disease. Genetic diversity at their DLA-DRB1, -DQA1, and -DQB1 loci were defined and potential association to major histocompatibility complex II haplotypes and alleles was analyzed. Giant Schnauzers carrying the DLA-DRB1*01201/DQA1*00101/DQB1*00201 haplotype showed an increased risk (odds ratio of 6.5) for developing CLT. The same risk haplotype has, to date, been observed in three different breeds affected by this disease, Giant Schnauzer, Dobermann, and Labrador Retriever, indicating that it is a common genetic risk factor in a variety of breeds affected by this disease. Importantly, protection for development of the disease was found in dogs carrying the DLA-DRB1*01301/DQA1*00301/DQB1*00501 haplotype (odds ratio of 0.3).