A chromosomal region on ECA13 is associated with maxillary prognathism in horses

Multiple congenital musculoskeletal abnormalities in a mule foal: a case report

Musculoskeletal abnormalities in neonate equids represent a common condition, which includes angular limb deformities, defective carpal/tarsal bone ossification, contracted limb and mandibular/maxillary prognathism. The present case report described the presentation and surgical management of multiple musculoskeletal abnormalities in a mule foal. A newborn mule foal was presented for several musculoskeletal abnormalities, such as angular deviation from the sagittal plane of both carpal joints, hind limb ligament laxity, and severe mandibular prognathism. Surgical management of mandibular prognathism was then treated through the application of a tension orthodontic wire. Postoperatively, there was a significant improvement in the correction of mandibular malocclusion and no further correction was needed. Management of other anomalies was mainly conservative, with stall rest and exercise limitations, with a considerable improvement in the first month of life. Thus, jaw malformations might be observed also in mule foals, and might be associated with multiple congenital abnormalities. Early recognition, appropriate management, and surgical treatment were essential.

Comparison of Computed Tomography Assisted 3D Cephalometric Measurements in Straight Egyptian Arabian and Thoroughbred Horses

Dental malocclusions are commonly encountered in horses. The objective of this study was to report the normal cephalometric values from skull computed tomography (CT) scans of adult Straight Egyptian Arabian (SEAR) and thoroughbred (TB) horses and to compare differences in the measurements between the two breeds. Standing skull CTs were performed on 29 clinically normal adult horses (15 SEAR; 14 TB) and cephalometric measurements were taken. All 9 cephalometric measurements, as well as the interincisal angle, were found to be significantly greater in TB than SEAR (P < 0.05). TB were found to have significantly greater facial line: mandibular length (FL/ML) ratios compared to SEAR (P = 0.002) whereas for the maxillary cheek teeth length: ethmoidal line ratio (Mxa/EtL), SEAR were found to have significantly greater values than TB (P = 0.0007). SEAR cephalometric measurements, as well as certain ratios, differ significantly from TB and could have an impact on the development of dental malocclusions in this breed. Further investigation is needed to ascertain whether these cephalometric differences between the two breeds predispose the SEAR to the development of dental malocclusions.

WNT10B: A locus increasing risk of brachygnathia inferior in Brown Swiss cattle

Shortening of the mandible (brachygnathia inferior) is a congenital, often inherited and variably expressed craniofacial anomaly in domestic animals including cattle. Brachygnathia inferior can lead to poorer animal health and welfare and reduced growth, which ultimately affects productivity. Within the course of the systematic conformation scoring, cases with a frequency of about 0.1% were observed in the Brown Swiss cattle population of Switzerland. In contrast, this anomaly is almost unknown in the Original Braunvieh population, representing the breed of origin. Because none of the individually examined 46 living offspring of our study cohort of 145 affected cows showed the trait, we can most likely exclude a monogenic-dominant mode of inheritance. We hypothesized that either a monogenic recessive or a complex mode of inheritance was underlying. Through a genome-wide association study of 145 cases and 509 controls with imputed 624k SNP data, we identified a 4.5 Mb genomic region on bovine chromosome 5 significantly associated with this anomaly. This locus was fine-mapped using whole-genome sequencing data. A run of homozygosity analysis revealed a critical interval of 430 kb. A breed specific frameshift duplication in WNT10B (rs525007739; c.910dupC; p.Arg304ProfsTer14) located in this genomic region was found to be associated with a 21.5-fold increased risk of brachygnathia inferior in homozygous carriers. Consequently, we present for the first time a genetic locus associated with this well-known anomaly in cattle, which allows DNA-based selection of Brown Swiss animals at decreased risk for mandibular shortening. In addition, this study represents the first large animal model of a WNT10B-related inherited developmental disorder in a mammalian species.

Systematic review on the genetic factors associated with skeletal Class II malocclusion

AIM

The aim of this study is to review studies evaluating the role of genetics in skeletal class II malocclusion.

OBJECTIVE

To assess the scientific evidence associating the role of genes in skeletal class II malocclusion. Materials and Methods: A complete search across the electronic database through PubMed, Cochrane, LILACS, BMC and manual hand search of orthodontic journals were done till May 2019. The keywords for the search included: "Genetics", "class II malocclusion", "maxillary prognathism", "mandibular retrognathism".

DATA COLLECTION AND ANALYSIS

Studies were selected based on PRISMA guidelines.

RESULTS

Articles were selected based on the inclusion and exclusion criteria. A total of 11 cross-sectional studies satisfied the inclusion criteria and were analyzed for the role of genes in skeletal class II malocclusion. Almost all the studies except for one revealed a positive correlation of genes with skeletal class II malocclusion.

CONCLUSIONS

Out of the 11 studies included, a positive correlation of the genes with the skeletal II malocclusion was found in 10 studies. Genes FGFR2, MSX1, MATN1, MYOH1, ACTN3, GHR, KAT6B, HDAC4, AJUBA were found to be positively linked to skeletal class II malocclusion.

Orthodontics and Genetics

Introduction:

Genetics has been suggested as an explanation for the etiology of malocclusions, although some questions, due to the perception that genetic inheritance is tied to a monogenic or Mendelian form of inheritance.

Objective:

This paper describes the inheritance of malocclusions, highlighting the areas of knowledge where research has explored mechanisms that explain deviations in patterns of craniofacial growth.

Conclusion:

Malocclusions have a complex or multifactorial pattern of inheritance, where more than one gene is involved in the development of the phenotype. There is also the possibility that the environment influences malocclusions.

Cephalometric Study of the Overjet Development in Warmblood Foals

Class II malocclusion is the most frequently occurring congenital malocclusion in horses. Radiographic cephalometric procedures adopted from human dentistry were used to study the development of overjet in a population of 650 Warmblood foals. Thirteen foals were diagnosed with measurable overjet at the beginning of the study. The malocclusion in nine foals resolved spontaneously and four foals without overjet at 2 weeks of age developed the condition during the first year of life. A cephalostat used in human orthodontics to immobilize the patient's head while being radiographed was replaced by a researcher-made head-holding device, whose size was based on the results of a pilot study. Laterolateral digital radiographs of each foal's head (cephalograms) were taken at five time points until the age of 12 months. Thirteen cephalometric points were identified and nine distances were measured on each radiograph. Additionally, the angle between the long axis of the upper and lower incisors was evaluated. Cephalometric measurements proved to be useful to identify foals that showed spontaneous regression of the malocclusion over the study time between 9 and 16 weeks of age.

Ten years of the horse reference genome: insights into equine biology, domestication and population dynamics in the post-genome era

The horse reference genome from the Thoroughbred mare Twilight has been available for a decade and, together with advances in genomics technologies, has led to unparalleled developments in equine genomics. At the core of this progress is the continuing improvement of the quality, contiguity and completeness of the reference genome, and its functional annotation. Recent achievements include the release of the next version of the reference genome (EquCab3.0) and generation of a reference sequence for the Y chromosome. Horse satellite‐free centromeres provide unique models for mammalian centromere research. Despite extremely low genetic diversity of the Y chromosome, it has been possible to trace patrilines of breeds and pedigrees and show that Y variation was lost in the past approximately 2300 years owing to selective breeding. The high‐quality reference genome has led to the development of three different SNP arrays and WGSs of almost 2000 modern individual horses. The collection of WGS of hundreds of ancient horses is unique and not available for any other domestic species. These tools and resources have led to global population studies dissecting the natural history of the species and genetic makeup and ancestry of modern breeds. Most importantly, the available tools and resources, together with the discovery of functional elements, are dissecting molecular causes of a growing number of Mendelian and complex traits. The improved understanding of molecular underpinnings of various traits continues to benefit the health and performance of the horse whereas also serving as a model for complex disease across species.

Treatment of class 2 malocclusion by corrective osteotomy using two short locking compression plates

Objective

To describe a symphyseal osteotomy stabilised with two short locking compression plates (LCPs) for treatment of class 2 malocclusions.

Study design

Case series.

Methods

Five horses (age range 8 months to 5¾ years) with overjets and/or overbites ranging from 6 to 32 mm and from 0 to 60 mm, respectively, were treated by osteotomy through the caudal third of the mandibular symphysis, cranial to the interdental space. After cranial distraction and ventral rotation of the rostral part of the mandible, two short (5/6 hole), bent 3.5 mm LCPs were applied ventro‐laterally and secured with two or three locking screws on each side of the osteotomy. In one case, the osteotomy gap was filled with bone marrow.

Results

Final outcome was good to excellent. Two cases needed a second corrective surgery, one because of non‐occlusion of the cheek teeth and another because of abaxial deviation of the rostral portion of the mandible. In three cases with a persistent fistula, LCPs were removed after bridging; drainage resolved and wounds healed. The time to bridging of the osteotomy gap ranged from 2 to 6.5 months. The procedure is technically challenging. It is important that the incisors are well aligned, which proved to be difficult when there was an abnormal maxillary incisor arcade. Incisors should not make contact when LCPs are fixed. The cheek teeth, however, should have good occlusion after positioning and fixation of the LCPs. Endodontic treatment of open incisor pulp cavities may be helpful.

Main limitations

The study population was small and relatively heterogeneous in severity. A larger population with more severe cases might have allowed for a more definitive assessment of the value of the technique for clinical practice.

Conclusions

This technique can be used to achieve a good correction for class 2 malocclusions. The approach provides adequate stability with smaller implants than other published techniques that require transection of both rami. The technique is less invasive and preserves the roots of the incisors and cheek teeth, as well as the mandibular canal.

Study of the relationship between overjet development and some skull bone measurements in Warmblood foals

Overjet is defined as the projection of the maxillary incisors labial to their antagonists in a horizontal direction. This malocclusion in horses can lead to incorrect dental wear and is aesthetically undesirable. Whether lengthening of the maxilla or shortening of the mandible causes the condition has not yet been determined. Therefore, a measurement technique was developed to investigate the correlations between skull bone measurements in overjet-affected individuals. The position of the incisors in 650 Warmblood foals born in a private German stud was examined at two weeks of age, revealing the prevalence of overjet to be 2 per cent. Five measurements were made on each foal's head and comparisons with a second set of measurements that were made later in the foals first year showed a change in the presence or degree of overjet over time. Nine of 13 foals diagnosed with measurable overjet at the beginning of the study resolved spontaneously. Thirteen foals had no evidence of overjet at birth, of which four developed the condition during the first year of life. The methods used for measuring longitudinal changes in different skull bones and for the assessment of malocclusion in foals affected with overjet were considered effective.

An integrated genomic approach for the study of mandibular prognathism in the European seabass (Dicentrarchus labrax)

Skeletal anomalies in farmed fish are a relevant issue affecting animal welfare and health and causing significant economic losses. Here, a high-density genetic map of European seabass for QTL mapping of jaw deformity was constructed and a genome-wide association study (GWAS) was carried out on a total of 298 juveniles, 148 of which belonged to four full-sib families. Out of 298 fish, 107 were affected by mandibular prognathism (MP). Three significant QTLs and two candidate SNPs associated with MP were identified. The two GWAS candidate markers were located on ChrX and Chr17, both in close proximity with the peaks of the two most significant QTLs. Notably, the SNP marker on Chr17 was positioned within the Sobp gene coding region, which plays a pivotal role in craniofacial development. The analysis of differentially expressed genes in jaw-deformed animals highlighted the “nervous system development” as a crucial pathway in MP. In particular, Zic2, a key gene for craniofacial morphogenesis in model species, was significantly down-regulated in MP-affected animals. Gene expression data revealed also a significant down-regulation of Sobp in deformed larvae. Our analyses, integrating transcriptomic and GWA methods, provide evidence for putative mechanisms underlying seabass jaw deformity.

Heritabilities of health traits in Swiss Warmblood horses

REASONS FOR PERFORMING STUDY

There is a lack of evidence regarding genetic parameters of health traits in Swiss Warmblood horses.

OBJECTIVES

To estimate heritabilities of equine sarcoid disease, horn quality of hooves, prognathism and increased filling of talocrural joints as a possible indicator for osteochondrosis in Swiss Warmblood horses examined at the field tests for 3-year-olds between 2005 and 2013.

STUDY DESIGN

Retrospective analysis of breed society database.

METHODS

Swiss Warmblood horses were examined clinically by 13 veterinarians at field tests in Switzerland between 2005 and 2013. The presence of sarcoids, horn quality of the hooves, incisor occlusion and increased joint filling were assessed and recorded. Records of 3715 horses were integrated in a pedigree comprising 217,282 horses. Variance components and heritabilities were estimated on the liability scale using multiple-trait Gibbs sampler for animal models (MTGSAM).

RESULTS

The prevalences of the examined traits were rather low ranging from 2.4 to 13.0%. Heritabilities estimated were 0.21 ± 0.07 for the occurrence of sarcoids, 0.04 ± 0.02 for hooves with markedly brittle and friable horn quality, 0.03 ± 0.01 for hooves with marked growth ring formation, 0.06 ± 0.03 for prognathism and 0.08 ± 0.04 for increased filling of the talocrural joint (an indicator of possible osteochondrosis). The influence of the examiner on the variance of these observations was considerable.

CONCLUSIONS

With the exception of equine sarcoid disease, estimates for the heritabilities for the traits examined here were low. A standardised examination protocol may reduce the variance due to the examiner.

Imputation of sequence level genotypes in the Franches-Montagnes horse breed

BACKGROUND

A cost-effective strategy to increase the density of available markers within a population is to sequence a small proportion of the population and impute whole-genome sequence data for the remaining population. Increased densities of typed markers are advantageous for genome-wide association studies (GWAS) and genomic predictions.

METHODS

We obtained genotypes for 54 602 SNPs (single nucleotide polymorphisms) in 1077 Franches-Montagnes (FM) horses and Illumina paired-end whole-genome sequencing data for 30 FM horses and 14 Warmblood horses. After variant calling, the sequence-derived SNP genotypes (~13 million SNPs) were used for genotype imputation with the software programs Beagle, Impute2 and FImpute.

RESULTS

The mean imputation accuracy of FM horses using Impute2 was 92.0%. Imputation accuracy using Beagle and FImpute was 74.3% and 77.2%, respectively. In addition, for Impute2 we determined the imputation accuracy of all individual horses in the validation population, which ranged from 85.7% to 99.8%. The subsequent inclusion of Warmblood sequence data further increased the correlation between true and imputed genotypes for most horses, especially for horses with a high level of admixture. The final imputation accuracy of the horses ranged from 91.2% to 99.5%.

CONCLUSIONS

Using Impute2, the imputation accuracy was higher than 91% for all horses in the validation population, which indicates that direct imputation of 50k SNP-chip data to sequence level genotypes is feasible in the FM population. The individual imputation accuracy depended mainly on the applied software and the level of admixture.