Peter B. Cserhalmi-Friedman

Exposing the human nude phenotype.

The recent discovery of the human counterpart of the hairless mouse phenotype has helped our understanding of the molecular genetics of hair growth. But there are no reports of a defect in the human homologue of the best known of the ‘bald’ mouse phenotypes, the nude mouse. This may be because affected individuals are so gravely ill from the accompanying immunodeficiency that their baldness goes unnoticed. We have carried out a genetic analysis that reveals a human homologue of the nude mouse.

Trans-gender induction of hair follicles

Human follicle cells can be induced to grow in an incompatible host of the other sex.

Trans-species hair growth induction by human hair follicle dermal papillae.

Abstract: A series of experimental bioassays has shown that the dermal papilla of the adult rodent vibrissa hair follicle retains unique inductive properties. In view of the many phenotypic and functional differences between specific hair follicle types, and the growing interest in hair follicle biology and disease, it remains important to establish that the human hair follicle dermal papilla has equivalent capabilities. In this study we tested the ability of human hair follicle papillae to induce hair growth when implanted into transected, athymic mouse vibrissa follicles. The implanted papillae that interacted with mouse follicle epithelium created new fibre‐producing follicle end bulbs. The origin of the papillae in the recombinant structures was confirmed using laser capture microdissection and human specific gender determination by PCR. The demonstration that intact adult human dermal papillae can induce hair growth has implications for molecular analysis of basic hair growth mechanisms, particularly since the study involved common epithelial–mesenchymal signalling and recognition properties across species. It also improves the prospects for a cell‐based clinical approach to hair follicle disorders.

Preimplantation genetic diagnosis in two families at risk for recurrence of Herlitz junctional epidermolysis bullosa

Abstract: The Herlitz type of junctional epidermolysis bullosa (H‐JEB) is a severe inherited bullous disease which leads to the early demise of the affected newborn. Mutations in the genes encoding the 3 polypeptides of the anchoring filament protein laminin 5 underlie this condition. We studied 2 families with affected children who previously died from H‐JEB. Mutation screening using heteroduplex analysis and direct sequencing of the PCR products revealed a previously described hotspot mutation in LAMB3 (R635X), and a novel delayed termination codon in LAMB3 in the first proband. In the second proband, we found a novel initiation codon mutation in LAMB3, and a novel 2 bp deletion in LAMB3. For preimplantation genetic diagnosis (PGD) in these families, we developed nested multiplex PCR assays, amplifying the mutations and informative intragenic polymorphisms in the probands. Single embryonic cells were biopsied from 8‐cell embryos using standard techniques, and subjected to the multiplex PCR assay followed by restriction enzyme digestion. Embryos found not to carry either mutation were transferred to the mothers, and a pregnancy was established in the second family as evidenced by the elevated level of HCG, although the pregnancy did not persist. This study illustrates the feasibility of PGD for an inherited skin disorder for the first time.

A novel missense mutation in the COL7A1 gene underlies epidermolysis bullosa pruriginosa

Epidermolysis bullosa (EB) pruriginosa is a subtype of dominant dystrophic EB (DDEB), characterized by severe pruritus and blistering localized to the extensor surface of the extremities. EB pruriginosa exhibits extensive clinical heterogeneity with variable expression and delayed age of onset. Mutations in the COL7A1 gene, especially in glycine residues within Gly‐X‐Y repeats, have been shown to cause this form of DDEB. Here, we report a novel COL7A1 mutation in a Taiwanese pedigree with EB pruriginosa. Using PCR and direct sequence analysis we have identified a G→T transversion at nucleotide 7097 in exon 92 of COL7A1, converting a glycine residue to valine (G2366V). The mutation resides within a consecutive, uninterrupted stretch of 17 Gly‐X‐Y residues in the triple‐helical domain of type VII collagen. Interestingly, an affected member of this family also displayed elevated IgE levels, previously reported in some patients with this disorder. Our finding further implicates COL7A1 mutation in the pathogenesis of EB pruriginosa and underscores the heterogeneous clinical symptoms of glycine mutations in DDEB.

Identification of the glycine-to-arginine substitution G2043R in type VII collagen in a family with dominant dystrophic epidermolysis bullosa from Hungary

Abstract Epidermolysis bullosa (EB) represents a group of genodermatoses characterized by fragility and easy blistering of the skin. In the dystrophic forms of EB (DEB), blisters occur below the basement membrane, at the level of the anchoring fibrils. In the dominantly inherited forms (DDEB), the predominant type of mutation detected thus far is the substitution of a glycine residue which occurs within the collagenous domain of the molecule characterized by the repeating Gly‐X‐Y amino acid sequence. In this study, we searched for mutations in DDEB in a family from Hungary, by PCR amplification of segments of COL7A1, followed by heteroduplex analysis. Examination of the PCR fragment corresponding to exon 73 revealed a heteroduplex in affected individuals from the family. Sequence analysis revealed a G‐to‐A transition at nucleotide 6127 in the triple‐helical domain of COL7A1, which converted a glycine residue at amino acid position 2043 to an arginine. This report represents the second incidence of this mutation. G2043R. described first in a family with DDEB from Italy.

Characterization of the desmosomal cadherin gene family: genomic organization of two desmoglein genes on human chromosome 18q12.

Abstract: The human desmoglein genes, desmogleins 1–3, are members of the desmosomal cadherin superfamily, and encode critical components of the desmosome. These genes are tightly clustered within 150–200 kb of chromosome 18q12.1 and represent excellent candidate genes for genetic disorders of the epidermis linked to this region of the genome. Mutations in desmoglein 1 have already been implicated in the genetic disorder striate palmoplantar keratoderma. Similarly, a mutation in desmoglein 3 underlies the balding mouse phenotype, although no human mutations in desmoglein 3 have been identified to date. In this study, we have characterized the genomic organization of two of the three desmoglein genes mapped to chromosome 18q12. Comparison of their exon–intron structure reveals the high level of evolutionary conservation expected from these related genes. The identification of the genomic structure of the desmoglein genes will facilitate mutation detection in genodermatoses with desmosomal abnormalities resulting from underlying defects in these genes.

Identification of mutations in the transgluataminase 1 gene in lamellar ichthyosis

Abstract: Lamellar ichthyosis (LI) is an autosomal recessive disorder of cornification. Mutations in the transglutaminase 1 gene (TGM1) have been identified in several families with this disorder. We analyzed two unrelated families with offspring affected with LI. Family 1 included affected monozygotic twins, in which a homozygous G‐to‐T transversion was identified in exon 6 at amino acid residue R315L. This mutation was also identified in the unaffected mother. In family 2, which consisted of one affected infant, a T‐to‐G transversion in exon 8 resulted in a change of phenylalanine to valine, F400V, and a C‐to‐T transition in exon 4 resulted in a change of proline to leucine, P248L. In this family, the mutation F400V was found in the unaffected father, and the mutation P248L was identified in the unaffected mother. These findings extend the growing body of literature documenting mutations in the TGM1 gene as the molecular basis of certain cases of lamellar ichthyosis.

Identification of a glycine substitution and a splice site mutation in the type VII collagen gene in a proband with mitis recessive dystrophic epidermolysis bullosa

Dystrophic epidermolysis bullosa (DEB) is a genodermatosis characterized by fragility of the skin and mucous membranes. Underlying mutations in the DEB phenotype have been detected in the gene encoding type VII collagen (COL7A1), both in the dominant and recessive forms of DEB. In this study, we searched for mutations in a proband with a mild form of DEB by PCR amplification of segments of COL7A1, followed by heteroduplex analysis. Examination of PCR fragments corresponding to exons 3–4 and exons 51–53 revealed heteroduplexes. Direct sequencing of the PCR fragment containing exon 3 revealed a previously reported A-to-G transition in the 5′ donor splice site of exon 3 in the proband and in the clinically unaffected father, while direct sequencing of the PCR fragment containing exon 53 revealed a novel glycine substitution G1652R in the proband and in the clinically unaffected mother. Patients with relatively mild DEB and no family history are frequently diagnosed as a de novo case of dominant DEB, although a mild case of RDEB cannot be excluded on the basis of clinical and ultrastructural examination. We proved this case to be a recessively inherited disease. This information had a profound impact on the genetic counselling, because if the disease of the patient were to have had a new dominant mutation, he would have been counselled that the risk of his offspring being affected was one in two, but he could be accurately counselled that the risk of this offspring being affected was as low as the general population.

Paternal germline mosaicism in Herlitz junctional epidermolysis bullosa

Abstract: We studied a single patient with the lethal (Herlitz) type of junctional epidermolysis bullosa (H‐JEB). Screening for mutations in the LAMB3 gene in the patient revealed the previously described hotspot mutation R635X and a novel one basepair deletion in exon 10. The single basepair deletion 1094delA could be detected in the clinically unaffected mother, while the nonsense mutation R635X could not be found in the peripheral blood DNA of either parent. After excluding non‐paternity by microsatellite analysis using random markers on chromosomes 3, 8 and 18, we determined that the mutation R635X in the proband was most likely the result of a de novo event or alternatively, germline mosaicism. The parents requested prenatal diagnosis for a second pregnancy, and while the maternal mutation 1094delA could not be detected in DNA from the fetus, unexpectedly, the mutation R635X was present in the chorionic villus DNA. These findings were most consistent with paternal germline mosaicism for the recessive mutation R635X. The results have had a significant impact on the genetic counseling in this family. To our knowledge, this study represents the first documented case of germline mosaicism in junctional epidermolysis bullosa, and serves as a reminder that germline mosaicism should be considered in cases in which a ‘new’ mutation is found in the offspring of a clinically and/or genetically unaffected parent.