Kelly M. Credille

Mild recessive epidermolytic hyperkeratosis associated with a novel keratin 10 donor splice‐site mutation in a family of Norfolk terrier dogs

Background  Epidermolytic hyperkeratosis in humans is caused by dominant‐negative mutations in suprabasal epidermal keratins 1 and 10. However, spontaneous keratin mutations have not been confirmed in a species other than human.

Transglutaminase 1-deficient recessive lamellar ichthyosis associated with a LINE-1 insertion in Jack Russell terrier dogs

Background  Congenital, nonepidermolytic cornification disorders phenotypically resembling human autosomal recessive ichthyosis have been described in purebred dog breeds, including Jack Russell terrier (JRT) dogs. One cause of gene mutation important to humans and dogs is transposon insertions.

DNA sequence and physical mapping of the canine transglutaminase 1 gene

The transglutaminase 1 gene (TGM1) encodes an enzyme necessary for cross-linking the structural proteins that form the cornified envelope, an essential component of the outermost layer of the skin, the stratum corneum. Reported here is the complete coding region of canine TGM1, its chromosome localization, and its map position in the integrated canine linkage-radiation hybrid map. Canine TGM1 consists of 2,448 nucleotides distributed over 15 exons. The nucleotide sequence has 90% identity to human TGM1. The deduced canine TGM1 protein is 816 amino acids long and is 92% identical to human TGM1. Using fluorescence in situ hybridization, we localized canine TGM1 to dog (Canis familiaris) chromosome 8 (CFA 8q). Canine TGM1 localized to CFA 8 on the integrated linkage-radiation hybrid map in the interval FH2149–MYH7. Characterizing the coding region of canine TGM1 is a first step in examining the role of this enzyme in normal and defective cornification in the dog.

Preservation of phenotype in an organotypic cell culture model of a recessive keratinization defect of Norfolk terrier dogs.

Abstract:  The purpose of this study is to reproduce in vitro a recessive keratinization defect of Norfolk terrier dogs characterized by a lack of keratin 10 (K10) production. Keratinocytes from skin biopsy samples of four normal dogs and two affected dogs were cultured organotypically with growth factor‐supplemented media in order to stimulate cornification. The cultured epidermis from the normal dogs closely resembled the normal epidermis in vivo and cornified. The cultured epidermis from the affected dogs displayed many phenotypic alterations identified in skin biopsies from dogs with this heritable defect. Immunohistochemistry and immunoblotting showed a marked decrease in K10 from the cultures of the affected keratinocytes, compared to that in K10 from the cultures of the normal keratinocytes. Real‐time reverse transcription polymerase chain reaction quantitation showed a 31‐fold decrease in K10, a 1.75‐fold increase in K1 and a 136‐fold increase in K2e between the affected and the normal epidermis. Organotypic keratinocytes showed a 241‐fold decrease in K10, a 31‐fold decrease in K1 and a 1467‐fold decrease in K2e between the affected and normal cultures. Although in vitro keratin expression did not precisely simulate in vivo, the morphology of the normal and the affected epidermis was largely preserved; thus, this culture system may provide an alternative to in vivo investigations for cutaneous research involving cornification.

Digging up the canine genome – a tale to wag about

There is incredible morphological and behavioral diversity among the hundreds of breeds of the domestic dog, Canis familiaris. Many of these breeds have come into existence within the last few hundred years. While there are obvious phenotypic differences among breeds, there is marked interbreed genetic homogeneity. Thus, study of canine genetics and genomics is of importance to comparative genomics, evolutionary biology and study of human hereditary diseases. The most recent version of the map of the canine genome is comprised of 3,270 markers mapped to 3,021 unique positions with an average intermarker distance of ∼1 Mb. The markers include approximately 1,600 microsatellite markers, about 1,000 gene-based markers, and almost 700 bacterial artificial chromosome-end markers. Importantly, integration of radiation hybrid and linkage maps has greatly enhanced the utility of the map. Additionally, mapping the genome has led directly to characterization of microsatellite markers ideal for whole genome linkage scans. Thus, workers are now able to exploit the canine genome for a wide variety of genetic studies. Finally, the decision to sequence the canine genome highlights the dog’s evolutionary and physiologic position between the mouse and human and its importance as a model for study of mammalian genetics and human hereditary diseases.

Comparative sequence analysis and radiation hybrid mapping of two epidermal type II keratin genes in the dog: keratin 1 and keratin 2e

In order to extend knowledge of the process of cornification across species and to be better able to recognize inborn errors in keratin synthesis in the dog, we describe the organization and chromosome mapping of canine KRT1 and KRT2E and compare these results to human and murine sequence data. The coding regions of KRT1 and KRT2E are 1,860 bp and 1,902 bp respectively, distributed over nine exons. Both genes are localized on the canine radiation hybrid map to chromosome 27 in the type II keratin gene cluster close to polymorphic markers. These genes are highly conserved across species and based on both genomic and amino acid sequences, canine KRT1 and KRT2E share greater homology with humans than with mice.

Comparative sequence analysis and radiation hybrid mapping of the canine keratin 10 gene

The type I keratin, K10, is expressed in epidermal keratinocytes undergoing terminal differentiation to form the stratum corneum, a barrier essential for life. In order to facilitate the study of keratinization disorders in the dog, the sequence and mapping of KRT10 is reported. The coding region of KRT10 is 1707 bp and is comprised of eight exons. Although the length of KRT10 has been reported to be polymorphic in humans, this was not observed in the eight domestic dog breeds studied, although one wild canid displayed a size difference. The structure and sequence of this gene is highly conserved across mammalian species. Canine K10 had an 86% amino acid identity with the human gene. KRT10 was localized to the on-going canine radiation hybrid map to chromosome 9 in the type I keratin gene cluster.