Association of a variant upstream of Growth differentiation factor 11 (GDF11) on carcass traits in crossbred beef cattle

The mature peptide of growth differentiation factor 11 (GDF11) in Bos taurus breeds, shares 90% amino acid sequence similarity to myostatin (MSTN), where loss-of-function mutations result in muscular hyperplasia causing a phenotype known as double-muscling. Mutations in the MSTN coding sequence increase muscle mass and reduce fat and bone tissues, but also confer poor fertility, reduced stress tolerance, and increased calf mortality. GDF11 influences skeletal muscle development in mice, and muscular atrophy can be induced by exogenous GDF11 treatment. To date, there are no reports of GDF11’s role in bovine carcass traits. To determine associations between GDF11 and carcass quality in beef cattle, bovine GDF11 was examined in crossbred Canadian beef cattle populations during finishing. Few coding variants were found in this functionally important gene, but an upstream variant c.1-1951C>T (rs136619751) with a minor allele frequency of 0.31 was identified and further genotyped in two separate populations of crossbred steers (n=415 and 450). CC animals had lower backfat thickness, marbling percentage, and yield score than CT or TT animals (P <0.001 and <0.05). These data suggest a role of GDF11 in carcass quality in beef cattle and may provide a selection tool to improve carcass traits in cattle.

BMP3 is a novel locus involved in the causality of ocular coloboma

Coloboma, a congenital disorder characterized by gaps in ocular tissues, is caused when the choroid fissure fails to close during embryonic development. Several loci have been associated with coloboma, but these represent less than 40% of those that are involved with this disease. Here, we describe a novel coloboma-causing locus, BMP3. Whole exome sequencing and Sanger sequencing of patients with coloboma identified three variants in BMP3, two of which are predicted to be disease causing. Consistent with this, bmp3 mutant zebrafish have aberrant fissure closure. bmp3 is expressed in the ventral head mesenchyme and regulates phosphorylated Smad3 in a population of cells adjacent to the choroid fissure. Furthermore, mutations in bmp3 sensitize embryos to Smad3 inhibitor treatment resulting in open choroid fissures. Micro CT scans and Alcian blue staining of zebrafish demonstrate that mutations in bmp3 cause midface hypoplasia, suggesting that bmp3 regulates cranial neural crest cells. Consistent with this, we see active Smad3 in a population of periocular neural crest cells, and bmp3 mutant zebrafish have reduced neural crest cells in the choroid fissure. Taken together, these data suggest that Bmp3 controls Smad3 phosphorylation in neural crest cells to regulate early craniofacial and ocular development.

153 Differences in Health and Carcass Characteristics of Yearling Steers That Received Free-choice Garlic-infused Mineral Supplements

Garlic products have been reported to have antimicrobial effects and may trigger anemia in horses, but their direct impact on feedlot cattle has not been detailed. With increased free-choice feeding of garlic-infused mineral supplements to beef cattle, it is important to evaluate this strategy’s impact on the animals’ health and the potential impact on carcass qualities. This 2-yr study recruited 208 crossbred feedlot steers in a supplementation trial using a completely randomized design. Each year, 104 steers were assigned to 1 of 4 groups that received either non-garlic mineral supplement (MS), MS + 0.3% garlic-oil-based premix (GOil), MS + 2.5% garlic powder (LGP), MS + 5% garlic powder (HGP). Feed and supplements were provided on an ad-lib basis and were measured for each steer with automatic feeding units. The study evaluated health indicators such as blood parameters and internal parasites. At harvest, carcass characteristics (including the incidence of liver abscesses) were assessed for all steers. The groups consumed between 156 and 208 g/d of the supplement over the two years, with the MS group having a lower overall supplement intake than other groups. The average daily consumption of garlic products in GOil, LGP, and HGP were approximately 0.6g/d, 5.2g/d, and 10.1g/d, respectively. There was no difference in total fecal egg counts (P = 0.45) among the groups. There was no association between the treatment groups and incidences of liver abscess scores (P = 0.10) nor carcass grade outcomes (P = 0.84). Further, there were no differences in hot carcass weight (P = 0.90), rib eye area (P = 0.34) and carcass backfat thickness (P = 0.99). All blood parameters evaluated were within normal ranges for all groups. The results suggest that infusing commercial garlic products into mineral supplements is not associated with undesirable effects on cattle health or carcass characteristics.

151 Intake, Growth, and Insectifugal Outcomes Associated with Free-choice Supplementation of Garlic Products to Feedlot Steers

Conflicting anecdotal accounts from producers about their cattle performance and fly-repellence outcomes while receiving garlic-infused supplements have limited feeding decisions. This study evaluated differences in animal performance and insectifugal outcomes among four groups (26 steers per group) over two years (total = 208 steers). The steers either received non-garlic mineral supplement (MS), MS+0.3% garlic oil-based premix (GOil), MS+2.5% garlic powder (LGP), or MS+5% garlic powder (HGP). A completely randomized design was implemented where each steer was assigned to each treatment group while balancing for bodyweight and breed composition. Steers received a feedlot ration and free-choice mineral supplement for 86 and 108 d in the first and second year, respectively. Individual feed and supplement consumption were measured with automatic feeding units. Fly abundance on each animal was determined using digital images collected during weekly fly surveys. The ADG, feed efficiency, ultrasound body composition, and intake-related activities were also evaluated during the study. Data were analyzed using linear- or generalized linear mixed models in SAS. A significant year and Group×year interactions were observed for daily supplement intake (P < 0.02). Similar interactions (P < 0.04) were observed for feeding behaviors associated with supplement intake. Fly abundance during the peak months was below the economic threshold and was not different among the groups (P = 0.25), but the year and Group×year interactions were significant (P < 0.02). There were no differences among the groups for DMI (P = 0.81), ADG (P = 0.54) and gain to feed ratio (P = 0.34). The Group×year interactions were present for the change in ultrasound rib-fat-thickness. The reasons behind the differences in supplement intake are not clear but may be related to the garlic products’ phytochemical profiles. These results suggest that further studies are required to identify the specific bioactive compounds in garlic that affect supplement intake.

118 A comparison of intravaginal progesterone devices for fixed-time artificial insemination in beef cattle

Intravaginal progesterone (P4) devices used for ovarian synchronization before fixed-time AI (FTAI) differ in drug release, which may influence fertility outcome. A 2×2 study was designed to determine the effects of different intravaginal devices (PRID Delta, 1.55g of P4 vs. CIDR, 1.38g of P4) and parity (heifers vs. cows) on follicular dynamics, expression of oestrus, and pregnancy per AI (P/AI). At random stages of the oestrous cycle, nulliparous beef heifers and lactating cows were given 100µg of gonadorelin (gonadotrophin-releasing hormone, GnRH) intramuscularly (IM) and assigned randomly to either the PRID (n=76 heifers, 76 multiparous, 27 primiparous) or CIDR (n=76 heifers, 73 multiparous, 32 primiparous) group. Devices were removed 5 days later, an oestrus-detection patch was applied just cranial to the tail head, and 500µg of cloprostenol was given IM at the time of device removal and again 24h later. At 72h after device removal, cattle were inseminated and given 100µg of GnRH IM. Transrectal ultrasonography was used to determine the diameter of the largest follicle on the day of device removal and at FTAI, ovulation time, and pregnancy status 30 days after FTAI. A colour change of ≥50% of the oestrus-detection patch at FTAI was taken as expression of oestrus. Data were compared among groups by 2-way ANOVA using MIXED and GLIMMIX procedures. There were no interactions between P4 device and parity for any endpoint. The diameter of the largest follicle (mean±s.e.m.) was not different between PRID and CIDR groups on either the day of device removal (10.6±0.1 vs. 10.9±0.1mm) or the day of FTAI (13.7±0.1 vs. 13.9±0.1mm). The proportion displaying oestrus did not differ between P4 device groups, but was greater in heifers than in cows [121/152 (79.6%) vs. 135/207 (65.2%); P<0.01], and the interval from FTAI to ovulation was shorter in heifers than in cows (27.8±1.2 vs. 32.0±1.1 h; P=0.01). The P/AI was not different between P4 device groups or parity groups (overall 67.0%, 238/355). However, among lactating cows, the P/AI tended to be greater in the PRID vs. CIDR group [75/102 (73.5%) vs. 64/105 (61.0%); P=0.10], and was greater in multiparous vs. primiparous cows [106/148 (71.6%) vs. 33/59 (55.9%); P=0.04]. Among cattle that displayed oestrus, the P/AI tended to be greater in the PRID vs. CIDR group [92/123 (74.8%) vs. 85/131 (64.9%); P=0.09]. Among lactating cows that displayed oestrus, the P/AI was greater in multiparous vs. primiparous cows [74/94 (78.2%) vs. 24/42 (57.1%); P<0.01]. In summary, follicular dynamics and expression of oestrus did not differ between PRID and CIDR groups, but the P/AI tended to be greater in PRID-treated lactating cows and in cattle that displayed oestrus. This research was supported by CEVA Animal Health, Saskatchewan ADF, Agriculture and Agri-Foods Canada, and Rockway Inc.

Heterozygosity of the Celtic polled locus in Canadian scurred beef cattle

Polled cattle are preferable to horned or scurred animals because they are safer for handling and cause less bruising. Although DNA testing can determine horned/polled genotype, scurs may appear in polled animals. The inheritance of scurs is complex because it is a sex-influenced trait that interacts with the polled locus. We demonstrate that in 685 purebred and crossbred Canadian beef cattle, all 153 scurred animals were heterozygous polled at the Celtic variant. In addition, male obligate carriers of scurs were smooth polled when homozygous for the polled mutation. Scurred and non-scurred males were sequenced for five genes (CTDNEP1, SHBG, SOX15, FGF11, and DHRS7C) within the scur candidate region on BTA19 that are functionally related to bone development and hormone regulation. Multipoint linkage analysis was conducted using 18 microsatellite markers and two informative variants (DHRS7C g.29594018G>C and CTDNEP1 c.462G>A) in the scurred families and further supported mapping on BTA19 between BMS2142 (logarithm of the odds (LOD) = 5.42) and IDVGA46 (LOD = 3.47). These data indicate epistatic interactions between the scurred and polled loci and emphasise the necessity for a scurred DNA test to assist purebred beef producers in eradicating the scur trait.

85 DNA parentage in multi-sire breeding groups and sire repeatability on replacement heifer performance

The objective of this study was to apply DNA parentage testing in multi-sire breeding groups to assess repeatability of a sire’s impact on replacement females and terminal animals. Parentage testing was performed on DNA from 37 bulls and 1578 calves from a commercial ranch using natural breeding in four multi-sire breeding pastures over a four-year period (2015–2018). Parentage data was analyzed using Chi-square procedures. In 2016 and 2018, all bulls in the four breeding groups sired significantly different (P < 0.01) numbers of calves than expected. In 2015 and 2017, bulls in 2 of 4 and 3 of 4 breeding groups, respectively, sired significantly different (P < 0.01) numbers of calves than expected. For the 2015 and 2016 calf crops, three of 24 bulls used sired 30% of the calves and 33% of the selected replacement heifers. In 2017 and 2018, the calves born to the daughters of these three most prolific sires, averaged 4.5kg lower weaning weights than the average wean weights of the remaining calves. In 2018, all calves were tested for breed composition and vigour score using the EnvigourHX test from Neogen (Neogen Canada Inc., Edmonton Alberta, Canada). The average herd vigour score was 70%; the average vigour score for 2018 calves born to daughters of the top three prolific sires was 56%. Coupling production measures (weaning weights, birth dates, calving intervals) with sire parentage and vigour score data provides beef cattle producers with additional information to guide breeding choices to improve production in their operations.

PSIV-2 Investigating candidate scur genes in Bos taurus breeds

Scurs (loose horns) are inherited in a sex-influenced manner and are believed to appear in cattle when the animal is heterozygous (Pp) for the polled mutation. They are unwanted by beef producers, but are difficult to eradicate because scurs are epistatic to the polled mutation. With the development of a test for the 202 bp indel on BTA1 resulting in the polled phenotype in Celtic breeds, horned (pp) and polled (PP/Pp) animals can be genotyped at this locus. The aims of this study were: 1) to confirm the polled genotype in scurred families from a Canadian beef research herd (SCBRH), scurred cattle families from producers (SCFP), and polled and scurred feedlot steers using the Celtic poll test (PC), and 2) to identify new candidate genes between the recombinant genes of the postulated scur loci on BTA19. Through PCR amplification, the polled/horned genotype was confirmed in the SCBRH, SPCF, and 153 phenotyped feedlot steers with gel electrophoresis. One family from the SPCF, 26 scurred and 10 polled feedlot steers were genotyped as horned. Removing the SPCF horned animals from the scur loci mapping data changed the recombinant markers and created a new boundary, resulting in examination of five new candidate genes (CTDNEP1, FGF11, SOX15, SHBG, DHRS7C) based on function and position. To identify SNPs segregating with scurs, 16 animals were chosen from the PC genotyped feedlot steers, 8 Pp scurred steers and 8 Pp polled steers. Two SNP’s found in CTDNEP1 and DHRS7C were examined in the SCBRH with PCR-RFLP using BseRI and AciI, respectively, but did not segregate with scurs. In conclusion, careful phenotyping and genotyping for the polled/horned status of an animal should be confirmed for future studies to determine the genetic mutation resulting in scurs.

Contribution of growth differentiation factor 6-dependent cell survival to early-onset retinal dystrophies

Retinal dystrophies are predominantly caused by mutations affecting the visual phototransduction system and cilia, with few genes identified that function to maintain photoreceptor survival. We reasoned that growth factors involved with early embryonic retinal development would represent excellent candidates for such diseases. Here we show that mutations in the transforming growth factor-β (TGF-β) ligand Growth Differentiation Factor 6, which specifies the dorso-ventral retinal axis, contribute to Leber congenital amaurosis. Furthermore, deficiency of gdf6 results in photoreceptor degeneration, so demonstrating a connection between Gdf6 signaling and photoreceptor survival. In addition, in both murine and zebrafish mutant models, we observe retinal apoptosis, a characteristic feature of human retinal dystrophies. Treatment of gdf6-deficient zebrafish embryos with a novel aminopropyl carbazole, P7C3, rescued the retinal apoptosis without evidence of toxicity. These findings implicate for the first time perturbed TGF-β signaling in the genesis of retinal dystrophies, support the study of related morphogenetic genes for comparable roles in retinal disease and may offer additional therapeutic opportunities for genetically heterogeneous disorders presently only treatable with gene therapy.

Mutation of the bone morphogenetic protein GDF3 causes ocular and skeletal anomalies

Ocular mal-development results in heterogeneous and frequently visually disabling phenotypes that include coloboma and microphthalmia. Due to the contribution of bone morphogenetic proteins to such processes, the function of the paralogue Growth Differentiation Factor 3 was investigated. Multiple mis-sense variants were identified in patients with ocular and/or skeletal (Klippel-Feil) anomalies including one individual with heterozygous alterations in GDF3 and GDF6. These variants were characterized, individually and in combination, through integrated biochemical and zebrafish model organism analyses, demonstrating appreciable effects with western blot analyses, luciferase based reporter assays and antisense morpholino inhibition. Notably, inhibition of the zebrafish co-orthologue of GDF3 accurately recapitulates patient phenotypes. By demonstrating the pleiotropic effects of GDF3 mutation, these results extend the contribution of perturbed BMP signaling to human disease and potentially implicate multi-allelic inheritance of BMP variants in developmental disorders.

Incomplete penetrance and phenotypic variability characterize Gdf6-attributable oculo-skeletal phenotypes

Proteins of the bone morphogenetic protein (BMP) family are known to have a role in ocular and skeletal development; however, because of their widespread expression and functional redundancy, less progress has been made identifying the roles of individual BMPs in human disease. We identified seven heterozygous mutations in growth differentiation factor 6 (GDF6), a member of the BMP family, in patients with both ocular and vertebral anomalies, characterized their effects with a SOX9-reporter assay and western analysis, and demonstrated comparable phenotypes in model organisms with reduced Gdf6 function. We observed a spectrum of ocular and skeletal anomalies in morphant zebrafish, the latter encompassing defective tail formation and altered expression of somite markers noggin1 and noggin2. Gdf6(+/-) mice exhibited variable ocular phenotypes compatible with phenotypes observed in patients and zebrafish. Key differences evident between patients and animal models included pleiotropic effects, variable expressivity and incomplete penetrance. These data establish the important role of this determinant in ocular and vertebral development, demonstrate the complex genetic inheritance of these phenotypes, and further understanding of BMP function and its contributions to human disease.

A novel mechanistic spectrum underlies glaucoma-associated chromosome 6p25 copy number variation

The factors that mediate chromosomal rearrangement remain incompletely defined. Among regions prone to structural variant formation, chromosome 6p25 is one of the few in which disease-associated segmental duplications and segmental deletions have been identified, primarily through gene dosage attributable ocular phenotypes. Using array comparative genome hybridization, we studied ten 6p25 duplication and deletion pedigrees and amplified junction fragments from each. Analysis of the breakpoint architecture revealed that all the rearrangements were non-recurrent, and in contrast to most previous examples the majority of the segmental duplications and deletions utilized coupled homologous and non-homologous recombination mechanisms. One junction fragment exhibited an unprecedented 367 bp insert derived from tandemly arranged breakpoint elements. While this accorded with a recently described replication-based mechanism, it differed from the previous example in being unassociated with template switching, and occurring in a segmental deletion. These results extend the mechanisms involved in structural variant formation, provide strong evidence that a spectrum of recombination, DNA repair and replication underlie 6p25 rearrangements, and have implications for genesis of copy number variations in other genomic regions. These findings highlight the benefits of undertaking the extensive studies necessary to characterize structural variants at the base pair level.

GDF6, a novel locus for a spectrum of ocular developmental anomalies

Colobomata represent visually impairing ocular closure defects that are associated with a diverse range of developmental anomalies. Characterization of a chromosome 8q21.2-q22.1 segmental deletion in a patient with chorioretinal coloboma revealed elements of nonallelic homologous recombination and nonhomologous end joining. This genomic architecture extends the range of chromosomal rearrangements associated with human disease and indicates that a broader spectrum of human chromosomal rearrangements may use coupled homologous and nonhomologous mechanisms. We also demonstrate that the segmental deletion encompasses GDF6, encoding a member of the bone-morphogenetic protein family, and that inhibition of gdf6a in a model organism accurately recapitulates the proband's phenotype. The spectrum of disorders generated by morpholino inhibition and the more severe defects (microphthalmia and anophthalmia) observed at higher doses illustrate the key role of GDF6 in ocular development. These results underscore the value of integrated clinical and molecular investigation of patients with chromosomal anomalies.

Reduced human and murine corneal thickness in an Axenfeld-Rieger syndrome subtype

PURPOSE

Axenfeld-Rieger malformations of the anterior segment are clinically heterogeneous, and up to 50% of cases are attributable to PITX2 or FOXC1 mutation. In view of PITX2's contribution to corneal development and the altered CCT in some FOXC1-related cases, this study was undertaken to investigate whether a related phenotype is associated with the PITX2/Pitx2 mutation.

METHODS

Central corneal thickness (CCT) was measured in patients and mice with PITX2/Pitx2 mutations. CCT in affected individuals and unaffected first-degree relatives from a large PITX2 mutation pedigree was measured with ultrasonic pachymetry. For murine measurements, the optical coherence tomogram (OCT) was calibrated against plastic films whose thickness had been determined with scanning electron microscopy (SEM). Subsequently, CCT was measured in ex vivo eyes from Pitx2(+/-) and wild-type murine littermates by using OCT.

RESULTS

CCT in individuals with the PITX2 mutation (mean 484 microm; range, 425-519; n = 8) was significantly lower than in their unaffected first-degree relatives (mean 582 microm; range, 550-590; n = 5; P = 0.0002, t-test). Scanning electron microscopy (SEM) and OCT measurements of reference films correlated closely (r = 0.9995) and subsequent OCT analysis of murine eyes revealed a significant reduction in CCT in Pitx2(+/-) compared with wild-type littermates (Pitx2(+/-): mean, 72 microm; range, 57-87, n = 6; wt: mean, 88 microm; range, 63-100; n = 6, P = 0.035, t-test).

CONCLUSIONS

The results show that PITX2/Pitx2 mutation results in reduced corneal thickness and provides the first example of reduced CCT in a genetic subtype of glaucoma. These data will facilitate management of developmental glaucoma and offer potential for guiding molecular genetic testing in patients with Axenfeld-Rieger. The similar CCT reduction observed in patients and mice with comparable mutations emphasizes the utility of this murine model. The technical advance of optical murine CCT measurement also provides scope for serial in vivo imaging of the developing anterior segment and determining the effects of altered CCT on measured IOP.

Bovine spinal muscular atrophy: AFG3L2 is not a positional candidate gene

Bovine spinal muscular atrophy (BSMA) is a neurodegenerative disorder, which is widespread in Brown Swiss cattle. Main symptoms of the disease are muscular atrophy and recumbency. Affected calves die within few days or weeks. BSMA seems to be inherited as a recessive trait and the disease allele appears to have a common origin. In this study, a pedigree with 30 affected BSMA calves was used to genetically localize the BSMA locus. Linkage analysis was performed between microsatellite markers of seven chromosomes, where the homologous genes of human neurodegenerative disorders are located according to comparative mapping data, and the disease genotype. BSMA was mapped to chromosome 24 confirming the recently published localization (Medugorac et al. 2003). The candidate gene AFG3L2 was physically mapped to chromosome 24q24 using fluorescence in situ hybridization. Due to their different localizations AFG3L2 is not a positional candidate for BSMA. An informative marker localized on the telomeric side of the BSMA locus would be beneficial for marker-assisted selection as well as searching for the causative gene. However, finding a marker distal to BSMA locus is difficult because of its position at the end of the chromosome.

Inheritance of the F4ab, F4ac and F4ad E. coli receptors in swine and examination of four candidate genes for F4acR

Susceptibility to enterotoxigenic Escherichia coli with fimbriae F4ac is dominantly inherited in the pig. A three-generation pedigree was created to refine the position of F4acR on chromosome 13 comprising 202 pigs: eight parents, 18 F1 and 176 F2 pigs. The 17-point analysis indicates that F4acR lies between Sw207 and S0283. Recombinant offspring specify that the most probable order is Sw207-S0075-F4acR-Sw225-S0283. We observed six phenotypes for the three fimbrial variants F4ab, F4ac and F4ad. The two missing phenotypes F4abR-/F4acR+/F4adR+ and F4abR-/F4acR+/F4adR- indicate that pigs susceptible to F4ac are always susceptible to F4ab. Furthermore, a weak and a strong adhesion of F4ab and F4ad bacteria was observed. The weak receptor F4abR (F4abRw) was present only in pigs devoid of the receptor F4acR (F4abR+/F4acR-). In contrast, in pigs with the phenotype F4abR+/F4acR+, F4ab bacteria adhered to the majority of enterocytes. F4abRw constitutes a frequently observed phenotype whose inheritance is still unclear. Strong adhesion of F4ab and F4ac bacteria is most likely influenced by the same receptor that we name F4bcR. The number of F4ad bacteria that adhered to enterocytes was very variable in the adhesion test. Moreover, expression of F4adR was independent of age. Our segregation analyses indicated a dominant inheritance of F4adR, although the number of susceptible pigs was smaller than expected. We examined four genes as candidates for the F4acR locus: the transferrin receptor gene (TFRC) and three genes members of the glucosyl/galactosyltransferase family (B3GnT5, B3GALT3 and B4GALT4). Comparison of sequences from resistant and homozygous susceptible F4ac pigs did not reveal any causative single nucleotide polymorphism in the four genes. Two silent mutations at the positions 295 (C/T) and 313 (T/C) in B3GALT3 were found. Using the somatic cell hybrid panel, B3GnT5 and B3GALT3 were assigned to the chromosomal region SSC13q23-q41. No mutations were found in the cDNA sequences of these genes associated with the F4acR genotypes.