ABHD5 frameshift deletion in Golden Retrievers with ichthyosis.

Ichthyoses are hereditary skin disorders characterized by the formation of scales and defects in the outermost layer of the epidermis. In dogs, at least six different breed-specific ichthyoses including a relatively common PNPLA1-related autosomal recessive ichthyosis in Golden Retrievers are known. In this study, we investigated 14 Golden Retrievers with scales that were not homozygous for the mutant PNPLA1 allele suggesting a genetically distinct new form of ichthyosis. Histopathological examinations showed lamellar, orthokeratotic hyperkeratosis, and mildly hyperplastic epidermis that led to the diagnosis of a nonepidermolytic ichthyosis. Combined linkage and homozygosity mapping in 14 cases and 30 nonaffected family members delimited a critical interval of ∼12.7 Mb on chromosome 23. Whole-genome sequencing of an affected dog revealed a single protein-changing variant within this region that was not present in 795 control genomes. The identified variant is a 14 bp deletion in the ABHD5 gene (c.1006_1019del), leading to a frameshift and altering the last 14 codons p.(Asp336Serfs*6). The genotypes at this variant showed perfect cosegregation with the ichthyosis phenotype in a large family comprising 14 cases and 72 controls. ABHD5 encodes an acyltransferase required for lipid metabolism. In humans, variants in ABHD5 cause Chanarin-Dorfman syndrome, a neutral lipid storage disease with ichthyosis. Our data in dogs together with the knowledge on the effects of ABHD5 variants in humans strongly suggest ABHD5:c.1006_1019del as candidate causative genetic variant for a new canine form of ichthyosis, which we propose to designate as Golden Retriever ichthyosis type 2 (ICH2)

A Mutation in the SUV39H2 Gene in Labrador Retrievers with Hereditary Nasal Parakeratosis (HNPK) Provides Insights into the Epigenetics of Keratinocyte Differentiation.

Peer reviewe

Transcriptome Profiling and Differential Gene Expression in Canine Microdissected Anagen and Telogen Hair Follicles and Interfollicular Epidermis.

The transcriptome profile and differential gene expression in telogen and late anagen microdissected hair follicles and the interfollicular epidermis of healthy dogs was investigated by using RNAseq. The genes with the highest expression levels in each group were identified and genes known from studies in other species to be associated with structure and function of hair follicles and epidermis were evaluated. Transcriptome profiling revealed that late anagen follicles expressed mainly keratins and telogen follicles expressed GSN and KRT15. The interfollicular epidermis expressed predominately genes encoding for proteins associated with differentiation. All sample groups express genes encoding for proteins involved in cellular growth and signal transduction. The expression pattern of skin-associated genes in dogs is similar to humans. Differences in expression compared to mice and humans include BMP2 expression mainly in telogen and high KRT17 expression in the interfollicular epidermis of dogs. Our data provide the basis for the investigation of the structure and function of canine skin or skin disease and support the use of dogs as a model for human cutaneous disease by assigning gene expression to specific tissue states

Establishment and characterization of a canine keratinocyte organoid culture system

BACKGROUND: Perturbations of epidermal and follicular homeostasis have been attributed to a variety of skin diseases affecting dogs. The availability of an in vitro system to investigate these diseases is important to understand underlying pathomechanisms. OBJECTIVES: To establish an accurate and reliable in vitro 3D system of canine keratinocyte organoids to lay the basis for studying functional defects in interfollicular epidermis (IFE) and hair follicle (HF) morphogenesis, reconstitution and differentiation that lead to alopecic and epidermal diseases. ANIMALS: Skin biopsies were obtained from freshly euthanized dogs of different breeds with no skin abnormalities. METHODS: Cells derived from microdissected IFE and HFs were seeded in Matrigel and keratinocyte organoids were grown and characterized using immunohistochemistry, RT-qPCR and RNA sequencing. RESULTS: Both organoid lines develop into a basal IFE-like cell type. Gene and protein expression analysis revealed high mRNA and protein levels of keratins 5 and 14, IFE differentiation markers and intercellular molecules. Key markers of HF stem cells were lacking. Withdrawal of growth factors resulted in upregulation of markers such as KRT16, Involucrin, KRT17 and SOX9, showing the potential of the organoids to develop towards more differentiated tissue. CONCLUSION AND CLINICAL IMPORTANCE: Our 3D in vitro culture system provides the basis to explore epidermal function, to investigate the culture conditions necessary for the development of organoids with a HF signature and to address cutaneous disorders in dogs. However, for induction of HF signatures or hair growth, addition of different growth factors or co-culture with dermal papilla will be required

Percentage of small (<3mm²) and large (>3mm²) colonies derived from the upper isthmus and lower isthmus (n = 7 dogs).

<p>Total percentage of small and large colonies are put together in a column and sum up to 100% percent (n = 7).</p

Box plots depicting the range of colony numbers per cover slip growing from keratinocytes of telogen follicular compounds.

<p>Colonies derived from the upper isthmus and the lower isthmus (n = 7). The horizontal line within the box plots indicates the median of the samples. The edges of the box mark the first and third quartiles.</p

Estradiol-induced alopecia in five dogs after contact with a transdermal gel used for the treatment of postmenopausal symptoms in women

BACKGROUND Noninflammatory alopecia is a frequent problem in dogs. Estrogen-induced alopecia is well described in dogs, with estrogen producing testicular tumors and canine female hyperestrogenism. OBJECTIVES To increase awareness that extensive alopecia in dogs can be caused by exposure to estradiol gel used by owners to treat their postmenopausal symptoms. ANIMALS Skin biopsies from five dogs with extensive alopecia were examined. METHODS Owners were asked for a thorough case history, including possible exposure to an estradiol gel. Complete blood work and serum chemistry panel analysis were performed to investigate possible underlying causes. Formalin-fixed skin biopsy samples were obtained from lesional skin and histopathology was performed. RESULTS All owners confirmed the use of a transdermal estradiol gel and close contact with the affected dogs before development of alopecia. Histopathologic examination showed a similar picture in all five dogs. Most hair follicles were predominantly either in kenogen or telogen and hair follicle infundibula showed mild to moderate dilation. Hair regrowth was present in all five dogs after the exposure to the estradiol gel was stopped or minimized. Blood work and serum chemistry panel were within normal limits in all cases. One dog had elevated estradiol concentrations, whereas in another dog estradiol concentrations were within normal limits. CONCLUSION AND CLINICAL IMPORTANCE Alopecia can occur after contact with a transdermal gel used as treatment for postmenopausal symptoms in women. Estradiol gel used by female owners therefore represents a possible cause for noninflammatory alopecia in dogs. Estradiol concentrations are not necessarily elevated in affected dogs

Colony types with three different staining patterns.

<p>a) Colony type with mainly proliferative (Ki67+) cells. Note the small size and the irregular shape of the colony. b) Mixed colony type with both proliferative (Ki67+) and terminally differentiated (involucrin+) cells. c) Colony type with mainly terminally differentiated (involucrin+) cells. d-j) Higher magnification of a) depicting Ki67+ cells, involucrin+ cells and DAPI staining, respectively. e-k) Higher magnification of b) depicting Ki67+ cells, involucrin+ cells and DAPI staining, respectively. f-l) Higher magnification of c) depicting Ki67+ cells, involucrin+ cells and DAPI staining, respectively.a-c) Scale bar represents 500μm. d-l)Scale bar represents 200μm. Red: Ki67+ keratinocytes, green: Involucrin+ keratinocytes, blue: Nuclear staining (DAPI).</p

Bar plots representing the percentage of proliferative, mixed type and terminally differentiated colonies per cover slip.

<p>Colonies are derived from cells of the upper isthmus and the lower isthmus of telogen follicular compounds (n = 7). Red: Ki67+ colonies; green: involucrin+ colonies; red and green stripes: mixed type of colonies. The horizontal line within the box plots indicates the median of the samples. The edges of the box mark the first and third quartiles.</p

Colony types derived from compound anagen canine hair follicles on a 3T3 feeder layer.

<p>a) Colony derived from the upper isthmus. b) Colonies derived from the lower isthmus. c) Colonies derived from the bulbar region. Note confluency of the colonies derived from the bulbar region. Scale bar represents 100μm.</p