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Zusammenfassung Nach der Differenztheorie des Ekg. und der neuen Definition des einphasischen Aktionsstroms als elektrischer Ausdruck des Erregungsvorganges unter nur einer Ableitungsstelle muß es möglich sein, das diphasische Ekg. eines Herzstreifens durch Leitungsverzögerung in seine beiden monophasischen Komponenten zu zerlegen, so daß diese nacheinander und in entgegengesetzter Richtung zur Aufzeichnung kommen. Durch Behandlung der Zwischenstrecke mit Aqua dest. lassen sich solche Leitungsverzögerungen erreichen. Damit wurde der unmittelbare experimentelle Beweis für die Richtigkeit der Differenzkonstruktion (Differenzanalyse) des Ekg. erbracht.

Methods for parentage control in cattle have changed since their initial implementation in the late 1950s from blood group typing to single nucleotide polymorphism determination nowadays. In the early 1990s, a panel of 12 microsatellites was selected as international standard for parentage control and has been used since then, accompanied by international comparison tests ensuring permanent validity for the most common cattle breeds. Although nearly every parentage can be resolved using these microsatellites, cases with very close relatives became an emerging resolution problem during recent years. Thus, it must be presumed that although microsatellites have been selected based on their polymorphism information content and exclusion probabilities, and no direct selection against their variability was applied, other effects have induced a trend to the fixation of alleles and monomorphism. To determine changes of allele frequencies and exclusion probabilities, we analyzed the development of these parameters for the 12 microsatellites from 2004 to 2014. 168,000 recorded Holstein Friesian cattle genotypes were evaluated. During this time certain alleles of nine microsatellites increased significantly (t-values > 5). When calculating the exclusion probabilities for 11 microsatellites, reduction was determined for the three situations, i.e., one parent is wrongly identified (p= 0.01), both parents are wrongly identified (p= 0.005), and the genotype of one parent is missing (p= 0.048). With the addition of BM1818 to the marker set in 2009, this development was corrected leading to significant increases in exclusion probabilities. Although, the exclusion probabilities for the three family situations using the 12 microsatellites are > 99%, the clarification of 142 relationships in 40,000 situations where one parent is missing will still be impossible. 25 sires were identified that are responsible for the most significant microsatellite allele increases in the population. The corresponding alleles are mainly associated with milk protein and fat yield, body weight at birth and weaning, as well as somatic cell score, milk fat percentage, and longissimus muscle area. Our data show that most of the microsatellites used for parentage control in cattle are not neutral DNA markers and are influenced by hitchhiking effects.

Congenital cataracts are opacities of the lens present from birth. Affected individuals suffer from loss of vision differing from moderately impaired up to total blindness. Until today, more than 255 genes have been described to harbor causative mutations for hereditary cataracts in humans. Identified mutations mostly affect genes coding for lens crystallins, but also membrane, cytoskeleton, and gap junction proteins, beaded filaments, growth, and transcriptional factors. Cataracts in cattle have been observed in different breeds as Holstein Friesian, Jersey, Hereford, Aberdeen Angus, Shorthorn, Ayrshire, and Romagnola. However, the genetic basis of cataract formation remained unknown in most cases. We investigated 31 cases of bilateral congenital cataract in Holstein Friesian cattle. Pedigree analysis revealed that 26 of 31 cases were paternal half siblings. 28 of 31 cases shared one common ancestor on the dam and sire site of the pedigree three to five generations earlier. A case-control study was performed using genotyping data of 26 cases and 88 controls to check for associations with the cataract phenotype. A genome-wide analysis using the Illumina BovineSNP50v2 BeadChip revealed an association on bovine chromosome 7 (BTA7) at position 12.4 Mb (Bonferroni-adjusted p-value: 1.85 × 10–32) and 6.2 Mb (p-value: 5.44 × 10–30). Regarding the proposed autosomal recessive inheritance, we searched for regions of extended homozygosity in cases. A 7.4 Mb interval from 5,675,621 to 13,146,547 on BTA7 (UMD_3.1) was detected covered by 80 single nucleotide polymorphism (SNP) loci, and does not contain any genes previously described as cataract causing. To assess the population frequency, the region was phased (Beagle v. 3.3.2) and inferred for the putative disease related haplotype. The frequency of carriers deduced from haplotyping was ∼0.4% in 25,000 randomly tested Holstein Friesian cattle. Within and around the region of extended homozygosity, we searched for positional-functional candidate genes. Four potential functional candidates strongly linked to lens development (NOTCH3, NXNL1, SMARCA4, DNMT1) were identified and analyzed by Sanger sequencing. Furthermore, 21 positional candidates solely based on their location and four genes weakly linked to eye development were selected. Nevertheless, all these genes had to be excluded as potentially disease causing, because none of the detected variants were unambiguously associated with the phenotype, and/or the detected variants had no effect on the amino acid sequence. Due to the lack of further candidate genes in the associated region, additional studies, such as whole genome resequencing of affected and related cattle, are planned to elucidate the disease-causing mutation.

With the introduction of genomic selection in modern cattle breeding programs, a huge amount of SNP data became available. A thorough analysis of these data led to the identification of significantly underrepresented or almost absent homozygous haplotypes in the genome of different cattle breeds, so-called recessive (lethal) haplotypes. In Holstein Friesian (HF) more than 15 such lethal haplotypes (HHx) have been detected, however, only a few have been elucidated so far. Among the unsolved haplotypes, HH5, reported to be located in the interval between 91.8–93.8Mb on BTA9, has been traced back to Thornlea Texal Supreme born in 1957. In the German HF population a population frequency of as high as ∼4.8% was determined. To clarify the underlying mutation, DNA of BAC clones spanning the reported region were hybridized with genomic DNA of known imputed haplotype carriers and unaffected controls. After target enrichment, samples were subjected to massive parallel sequencing on a NextSeq500 platform. The HH5 target region was sequenced with an average 150-fold base coverage per animal (STD:78). Data were aligned to the bovine genome build UMD_3.1 and evaluated for polymorphisms and copy number variations. The latter revealed a deletion of ∼138kb with a breakpoint and fusion between BTA9:93,232,651 and BTA9:93,370,998. The deletion breakpoints are flanked by bovine long interspersed nuclear elements Bov-B, located upstream, and L1ME3, located downstream, suggesting a homologous recombination/deletion event. The deleted region harbors only one reference gene, i.e., dimethyl-adenosine transferase 1, or transcription factor B1 mitochondrial (TFB1M), encoding for an essential protein for synthesis and function of the small ribosomal subunit of mitochondria, and therefore mitochondrial protein translation. Knock-out experiments in mice have shown that TFB1Mis irreplaceable, as TFB1M-/-mice die at Day 8.5 during embryonal development. The allelic frequency in randomly selected ∼2,000 HF cattle of the German population was 2.8%, which calculates to a carrier frequency of 5.5%. To reduce the amount of carrier in the HF population it is advisable to directly genotype the deletion underlying HH5.

Ohne Zusammenfassung: