GWAS Hits for Bilateral Convergent Strabismus with Exophthalmos in Holstein Cattle Using Imputed Sequence Level Genotypes

Bilateral convergent strabismus with exophthalmos (BCSE) is a malformation of the eyes and is recognized as a mild but progressive disorder that affects cattle in the first two years of life. This most likely inherited disorder is rarely described in cattle resembling autosomal dominantly inherited forms of human progressive external ophthalmoplegia (PEO). In German Braunvieh cattle, two linked genome regions were found that could be responsible for the development and/or progression of BCSE. The goal of this study was to phenotypically characterize BCSE in Holstein cattle from Germany and Switzerland as well as to identify associated genome regions by GWAS. The clinicopathological phenotype of 52 BCSE-affected Holstein cattle was in accordance with the phenotype described in German Braunvieh cattle, but in addition, signs of degeneration and cellular infiltration in the eye muscles were found. By using imputed sequence level genotype data, three genome-wide significant GWAS hits were revealed on different chromosomes that were not detected by initial GWAS based on high density SNP array data highlighting the usefulness of this approach for mapping studies. The associated genome regions include the ABCC4 gene as well as markers adjacent to the NCOR2 and DNAJC3 genes all illustrating possible functional candidate genes. Our results challenge a monogenic mode of inheritance and indicate a more complex inheritance of BCSE in Holstein cattle. Furthermore, in comparison to previous results from German Braunvieh cattle, it illustrates an obvious genetic heterogeneity causing BSCE in cattle. Subsequent whole genome sequencing (WGS)-based analyses might elucidate pathogenic variants in the future.

[Genetic heterogeneity and complexity of congenital heart defects]

Congenital heart defects are the most common birth defects, they account for approximately one third of all cases. They are clinically heterogeneous, vary widely in severity, treatability and prognosis and may occur as part of multiple developmental disorders, such as chromosome aberrations, microdeletion syndromes and monogenic diseases, or as isolated defects. Syndromic forms account for 25-40%, isolated forms for 60-75% of all cases. With conventional cytogenetic and next-generation molecular genetic methods, numerous genetic alterations have been identified in evolutionarily highly conserved genes of transcriptional regulators, signaling molecules and structural proteins, which are critical to normal cardiogenesis, mostly in cases with syndromic congenital heart defects. On the other hand, the genetic cause can be detected only in around 11% of isolated heart defects. The survival rate and life quality of patients with congenital heart defects have improved significantly in the last decades thanks to the remarkable development of prenatal, postnatal diagnostics as well as of heart and thoracic surgery of cardiovascular diseases. Since the number of patients, living into adulthood and reproductive age, is constantly increasing, the better understanding of the genetics of congenital heart defects may be crucial for the diagnosis, prognosis and positive family planning of patients. Orv Hetil. 2018; 159(17): 661-670.

Genetics of inherited human epilepsies

Major advances have recently been made in our understanding of the genetic basis of monogenic inherited epilepsies. Progress has been particularly spectacular with respect to idiopathic epilepsies, with the discovery that mutations in ion channel subunits are implicated. However, important advances have also been made in many inherited symptomatic epilepsies, for which direct molecular diagnosis is now possible, simplifying previously complex investigations, it is expected that identification of the genes implicated in familial forms of epilepsies will lead to a better understanding of the underlying pathophysiological mechanisms of these disorders and to the development of experimental models and new therapeutic strategies, in this article, we review the clinical and genetic data concerning most of the inherited human epilepsies.

Genetics of inherited human epilepsies

Major advances have recently been made in our understanding of the genetic basis of monogenic inherited epilepsies. Progress has been particularly spectacular with respect to idiopathic epilepsies, with the discovery that mutations in ion channel subunits are implicated. However, important advances have also been made in many inherited symptomatic epilepsies, for which direct molecular diagnosis is now possible, simplifying previously complex investigations, it is expected that identification of the genes implicated in familial forms of epilepsies will lead to a better understanding of the underlying pathophysiological mechanisms of these disorders and to the development of experimental models and new therapeutic strategies, in this article, we review the clinical and genetic data concerning most of the inherited human epilepsies.