A Heterozygous Missense Variant in the COL5A2 in Holstein Cattle Resembling the Classical Ehlers-Danlos Syndrome

Naturally occurring genetic diseases caused by de novo variants in domestic animals

With the advent of next-generation sequencing, an increasing number of cases of de novo variants in domestic animals have been reported in scientific literature primarily associated with clinically severe phenotypes. The emergence of new variants at each generation is a crucial aspect in understanding the pathology of early-onset diseases in animals and can provide valuable insights into similar diseases in humans. With the aim of collecting deleterious de novo variants in domestic animals, we searched the scientific literature and compiled reports on 42 de novo variants in 31 genes in domestic animals. No clear disease-associated phenotype has been established in humans for three of these genes (NUMB, ANKRD28 and KCNG1). For the remaining 28 genes, a strong similarity between animal and human phenotypes was recognized from available information in OMIM and OMIA, revealing the importance of comparative studies and supporting the use of domestic animals as natural models for human diseases, in line with the One Health approach.

Identification of an ADAMTS2 frameshift variant in a cat family with Ehlers-Danlos syndrome

We investigated 4 European domestic shorthair kittens with skin lesions consistent with the dermatosparaxis type of the Ehlers-Danlos syndrome, a connective tissue disorder. The kittens were sired by the same tomcat but were born by 3 different mothers. The kittens had easily torn skin resulting in nonhealing skin wounds. Both clinically and histologically, the skin showed thin epidermis in addition to inflammatory changes. Changes in collagen fibers were visible in electron micrographs. The complete genome of an affected kitten was sequenced. A one base pair duplication leading to a frameshift in the candidate gene ADAMTS2 was identified, p.(Ser235fs*3). All 4 affected cats carried the frameshift duplication in a homozygous state. Genotypes at this variant showed perfect cosegregation with the autosomal recessive Ehlers-Danlos syndrome phenotype in the available family. The mutant allele did not occur in 48 unrelated control cats. ADAMTS2 loss-of-function variants cause autosomal recessive forms of Ehlers-Danlos syndrome in humans, mice, dogs, cattle, and sheep. The available evidence from our investigation together with the functional knowledge on ADAMTS2 in other species allows to classify the identified ADAMTS2 variant as pathogenic and most likely causative variant for the observed Ehlers-Danlos syndrome.

ENTPD1-AS1–miR-144-3p-mediated high expression of COL5A2 correlates with poor prognosis and macrophage infiltration in gastric cancer

BACKGROUND

Gastric cancer (GC) is a malignant tumor with high morbidity and mortality. Expression of COL5A2 is significantly elevated in GC. Abnormal expression of noncoding RNAs (ncRNAs) have been found in GC, including microRNA (miRNA) and long noncoding RNA (lncRNA). Competing endogenous RNA network plays an important regulatory role in GC. However, its specific regulatory mechanism has not been elucidated.

AIM

To gain insight into the ncRNA regulatory mechanism and immune microenvironment related to COL5A2 in GC.

METHODS

RNA sequencing data and clinical information from The Cancer Genome Atlas data portal were used to analyze the expressions of COL5A2, miRNA and lncRNA related to the prognosis of GC. Cox regression analysis and Kyoto Encyclopedia of Genes and Genomes analysis were performed to assess the risk factors and relevant function of COL5A2. StarBase was used to predict the interaction of miRNA–lncRNA or miRNA–mRNA in GC. The relationship between COL5A2, miR-144-3p and ENTPD1-AS1 were verified by dual luciferase reporter assay. The association of COL5A2 with immune cell infiltration were analyzed using the Tumor Immune Estimation Resource database and single sample gene set enrichment analysis. The expression of COL5A2 and macrophages in paired GC tissues were detected by immunohistochemical staining.

RESULTS

We verified that the upregulation of COL5A2 expression was associated with the prognosis of GC and was an independent risk factor for GC. miR-144-3p was downregulated and correlated with the prognosis of GC. miR-144-3p regulated the expression of COL5A2 through direct interaction with COL5A2. ENTPD1-AS1 was elevated in GC and competitively bound to miR-144-3p, thus inhibiting the expression of miR-144-3p. ENTPD1-AS1 enhanced the expression of COL5A2 through sponging miR-144-3p. Compared to paired normal tissue, COL5A2 expression was upregulated at the protein level, especially in the middle and late stages of GC. The high expression of COL5A2 was positively linked to macrophage infiltration in GC.

CONCLUSION

COL5A2 regulated by ENTPD1-AS1–miR-144-3p was associated with poor prognosis and macrophage infiltration in GC. This could be a new biomarker and therapeutic target in GC.

A COL5A2 In-Frame Deletion in a Chihuahua with Ehlers-Danlos Syndrome

Ehlers-Danlos syndrome (EDS) is a group of heterogeneous, rare diseases affecting the connective tissues. The main clinical signs of EDS are skin hyperextensibility, joint hypermobility, and skin fragility. Currently, the classification of EDS in humans distinguishes 13 clinical subtypes associated with variants in 20 different genes, reflecting the heterogeneity of this set of diseases. At present, variants in three of these genes have also been identified in dogs affected by EDS. The purpose of this study was to characterize the clinical and histopathological phenotype of an EDS-affected Chihuahua and to identify the causative genetic variant for the disease. The clinical examination suggested a diagnosis of classical EDS. Skin histopathology revealed an abnormally thin dermis, which is compatible with classical EDS. Whole-genome sequencing identified a heterozygous de novo 27 bp deletion in the COL5A2 gene, COL5A2:c.3388_3414del. The in-frame deletion is predicted to remove 9 amino acids in the triple-helical region of COL5A2. The molecular analysis and identification of a likely pathogenic variant in COL5A2 confirmed the subtype as a form of classical EDS. This is the first report of a COL5A2-related EDS in a dog.

DSP missense variant in a Scottish Highland calf with congenital ichthyosis, alopecia, acantholysis of the tongue and corneal defects

BACKGROUND

Ichthyosis describes a localized or generalized hereditary cornification disorder caused by an impaired terminal keratinocyte differentiation resulting in excessive stratum corneum with the formation of more or less adherent scales. Ichthyosis affects humans and animals. Two rare bovine forms are reported, the severe harlequin ichthyosis and the less severe congenital ichthyosis, both characterized by a severe orthokeratotic lamellar hyperkeratosis.

RESULTS

A 2-weeks-old purebred Scottish Highland calf was referred because of a syndrome resembling congenital ichthyosis. The clinical phenotype included diffuse alopecia and a markedly lichenified skin covered with large and excessive scales. Additionally, conjunctivitis and ulceration of the cornea were noted. Post-mortem examination revealed deep fissures in the diffusely thickened tongue and histopathological findings in the skin confirmed the clinical diagnosis. Whole-genome sequencing of the affected calf and comparison of the data with control genomes was performed. A search for private variants in known candidate genes for skin phenotypes including genes related with erosive and hyperkeratotic lesions revealed a single homozygous protein-changing variant, DSP: c.6893 C>A, or p.Ala2298Asp. The variant is predicted to change a highly conserved residue in the C-terminal plakin domain of the desmoplakin protein, which represents a main intracellular component of desmosomes, important intercellular adhesion molecules in various tissues including epidermis. Sanger sequencing confirmed the variant was homozygous in the affected calf and heterozygous in both parents. Further genotyping of 257 Scottish Highland animals from Switzerland revealed an estimated allele frequency of 1.2%. The mutant allele was absent in more than 4800 controls from various other cattle breeds.

CONCLUSIONS

This study represents the first report of combined lesions compatible with congenital ichthyosis, alopecia, acantholysis of the tongue and corneal defects associated with a DSP missense variant as the most likely underlying cause. To the best of our knowledge, this study is also the first report of a DSP-related syndromic form of congenital ichthyosis in domestic animals. The results of our study enable genetic testing to avoid the unintentional occurrence of further affected cattle. The findings were added to the Online Mendelian Inheritance in Animals (OMIA) database (OMIA 002243-9913).

A frameshift insertion in FA2H causes a recessively inherited form of ichthyosis congenita in Chianina cattle

The aim of this study was to characterize the phenotype and to identify the genetic etiology of a syndromic form of ichthyosis congenita (IC) observed in Italian Chianina cattle and to estimate the prevalence of the deleterious allele in the population. Sporadic occurrence of different forms of ichthyosis including IC have been previously reported in cattle. However, so far, no causative genetic variant has been found for bovine IC. Nine affected cattle presenting congenital xerosis, hyperkeratosis and scaling of the skin as well as urolithiasis and cystitis associated with retarded growth were examined. Skin histopathology revealed a severe, diffuse orthokeratotic hyperkeratosis with mild to moderate epidermal hyperplasia. The pedigree records indicated a monogenic recessive trait. Homozygosity mapping and whole-genome sequencing allowed the identification of a homozygous frameshift 1 bp insertion in the FA2H gene (c.9dupC; p.Ala4ArgfsTer142) located in a 1.92 Mb shared identical-by-descent region on chromosome 18 present in all cases, while the parents were heterozygous as expected for obligate carriers. These findings enable the selection against this sub-lethal allele showing an estimated frequency of ~ 7.5% in Chianina top sires. A sporadic incidence of mild clinical signs in the skin of heterozygous carriers was observed. So far, pathogenic variants affecting the encoded fatty acid 2-hydroxylase catalyzing the synthesis of 2-hydroxysphingolipids have been associated with myelin disorders. In conclusion, this study represents the first report of an FA2H-related autosomal recessive inherited skin disorder in a mammalian species and adds FA2H to the list of candidate genes for ichthyosis in humans and animals. Furthermore, this study provides a DNA-based diagnostic test that enables selection against the identified pathogenic variant in the Chianina cattle population. However, functional studies are needed to better understand the expression of FA2H in IC-affected Chianina cattle.

Animal Models of Ehlers-Danlos Syndromes: Phenotype, Pathogenesis, and Translational Potential

The Ehlers-Danlos syndromes (EDS) are a group of heritable connective tissues disorders mainly characterized by skin hyperextensibility, joint hypermobility and generalized tissue fragility. Currently, 14 EDS subtypes each with particular phenotypic features are recognized and are caused by genetic defects in 20 different genes. All of these genes are involved in the biosynthesis and/or fibrillogenesis of collagens at some level. Although great progress has been made in elucidating the molecular basis of different EDS subtypes, the pathogenic mechanisms underlying the observed phenotypes remain poorly understood, and consequentially, adequate treatment and management options for these conditions remain scarce. To date, several animal models, mainly mice and zebrafish, have been described with defects in 14 of the 20 hitherto known EDS-associated genes. These models have been instrumental in discerning the functions and roles of the corresponding proteins during development, maturation and repair and in portraying their roles during collagen biosynthesis and/or fibrillogenesis, for some even before their contribution to an EDS phenotype was elucidated. Additionally, extensive phenotypical characterization of these models has shown that they largely phenocopy their human counterparts, with recapitulation of several clinical hallmarks of the corresponding EDS subtype, including dermatological, cardiovascular, musculoskeletal and ocular features, as well as biomechanical and ultrastructural similarities in tissues. In this narrative review, we provide a comprehensive overview of animal models manifesting phenotypes that mimic EDS with a focus on engineered mouse and zebrafish models, and their relevance in past and future EDS research. Additionally, we briefly discuss domestic animals with naturally occurring EDS phenotypes. Collectively, these animal models have only started to reveal glimpses into the pathophysiological aspects associated with EDS and will undoubtably continue to play critical roles in EDS research due to their tremendous potential for pinpointing (common) signaling pathways, unveiling possible therapeutic targets and providing opportunities for preclinical therapeutic interventions.