Mutation of the ectodysplasin-A gene results in bone defects in mice

Anhidrotic ectodermal dysplasia (EDA) is an X-linked, recessive genetic disease characterized by dysfunctional sweat glands, poorly developed teeth, and premature balding in human beings. This disorder results from mutations in the gene for ectodysplasin-A, a type II transmembrane protein with tumour necrosis factor-alpha domains. An animal model of EDA, the Tabby mouse, also has mutations in the ectodysplasin-A gene and defects similar to those of human beings with EDA. In addition to these defects, Tabby mice acquire deformities in the distal portion of their tails at 10-12 weeks of age. Whole-mount staining of the skeleton with Alizarin Red and Alcian Blue revealed that the tail defect resulted from vertebral fractures just distal to the epiphysis. Histological analysis demonstrated that the structure of both the epiphysis and the subepiphyseal zone of the tail vertebrae was dysplastic while the shaft of the diaphysis was relatively normal. The overall structure of the trabecular bone of these animals was examined through 3-dimensional microcomputed tomography of the tibia. This analysis indicated that Tabby mice had a mild increase in the interconnectivity of the intertwined trabecular bone network but that individual trabeculae were relatively normal. Since it has been determined recently that the ectodysplasin-A gene is expressed in the osteoblasts of developing human embryos, it appears likely that this gene plays a role in normal bone development.

Netherton syndrome: disease expression and spectrum of SPINK5 mutations in 21 families

Netherton syndrome is a severe autosomal recessive skin disorder characterized by congenital erythroderma, a specific hair-shaft abnormality, and atopic manifestations with high IgE levels. Recently, we identified SPINK5, which encodes the serine protease inhibitor Kazal-type 5 protein (LEKTI), as the defective gene in Netherton syndrome. Here we describe the intron-exon organization of the gene and characterize the SPINK5 mutations in patients from 21 families of different geographic origin, using denaturing high performance liquid chromatography and direct sequencing. We identified 18 mutations, of which 13 were novel and seven (39%) were recurrent. The majority of the mutations were clustered between exons 1-8 and exons 21-26. They comprised four nonsense mutations (22%), eight frameshift insertions or deletions (44%), and six splice-site defects (33%). All mutations predict the formation of premature termination codons. Northern blot analysis showed variable reduction of SPINK5 mutant transcript levels, suggesting variable efficiency of nonsense-mediated mRNA decay. Seven patients were homozygotes, eight were compound heterozygotes, and five were heterozygotes with only one identifiable SPINK5 mutation. Five mutations, one of which resulted in perinatal lethal disease in three families, were associated with certain ethnic groups. We also describe 45 intragenic polymorphisms in the patients studied. The clinical features of erythroderma, trichorrhexis invaginata, and atopic manifestations were present in the majority of affected individuals and ichthyosis linearis circumflexa was seen in 12 out of 24 patients. Interfamilial and intrafamilial variation in disease severity was observed, with no clear correlation between mutations and phenotype, suggesting that the degree of severity may be affected by other factors.

Hypohidrotic ectodermal dysplasia: dental, clinical, genetic and dermatoglyphic findings of three cases

Patients with hypohidrotic ectodermal dysplasia (HED) are characterized by the clinical manifestations of hypodontia, hypohidrosis, hypotrichosis and a highly characteristic facial physiognomy. This disorder is inherited as an X-linked trait. This report presents three cases with HED in which the clinical evaluation (intraoral and radiological), genetic findings and SEM examination of hair. Boys 6 to 14 year old and a 11 year old girl were referred to the Marmara University, Faculty of Dentistry, complaining of oligodontia in the maxillary and mandibular arches and delay in eruption of other teeth. Peg-shaped teeth have been observed. The dermatoglyphs of the patients were striking. SEM examination of hair demonstrated a distinctly abnormal longitudinal grooving along the entire length of each hair and a desquamation of the surface cuticles. The treatment was planned in a multidisciplinary odontological group involving pediatric dentistry, orthodontics, prosthodontics and oral surgery and maxillofacial radiology of future dental habilitation. A specially designed overdenture, a removable prosthesis and osseointegrated implants were constructed. Periodic recall visits were advised, to monitor the dentures and implants during periods of growth and development, and eruption of the permanent teeth.

p53 mutant mice that display early ageing-associated phenotypes

The p53 tumour suppressor is activated by numerous stressors to induce apoptosis, cell cycle arrest, or senescence. To study the biological effects of altered p53 function, we generated mice with a deletion mutation in the first six exons of the p53 gene that express a truncated RNA capable of encoding a carboxy-terminal p53 fragment. This mutation confers phenotypes consistent with activated p53 rather than inactivated p53. Mutant (p53+/m) mice exhibit enhanced resistance to spontaneous tumours compared with wild-type (p53+/+) littermates. As p53+/m mice age, they display an early onset of phenotypes associated with ageing. These include reduced longevity, osteoporosis, generalized organ atrophy and a diminished stress tolerance. A second line of transgenic mice containing a temperature-sensitive mutant allele of p53 also exhibits early ageing phenotypes. These data suggest that p53 has a role in regulating organismal ageing.

Leptin modulates the effects of acyl CoA:diacylglycerol acyltransferase deficiency on murine fur and sebaceous glands

Acyl CoA:diacylglycerol acyltransferase (DGAT) is a ubiquitously expressed enzyme that catalyzes the final reaction in the major pathways of triglyceride synthesis. Mice lacking DGAT1 (Dgat(-/-)) demonstrate significant changes in lipid metabolism in several tissues, including the skin. Here we report the effects of DGAT1 deficiency on fur and sebaceous glands. Adult Dgat(-/-) mice had dry fur and hair loss, which were associated with atrophic sebaceous glands and fur lipid abnormalities. As a result, Dgat(-/-) mice had impaired water repulsion and defective thermoregulation after water immersion. These phenotypes were mostly absent in Dgat(-/-) mice with leptin deficiency, indicating an unexpected role for leptin in modulating the skin phenotype. Our findings indicate that DGAT1 plays an important role in normal fur and sebaceous gland physiology and provide evidence that leptin modulates these processes in the skin.

A previously unreported syndrome of multiple scalp whorls and associated anomalies

A 13-month-old male infant with 14 hair whorls in the scalp, sparse frontal hair, wide forehead, ectropion, abnormal implantation of eyelashes, peculiar face and depigmented nipples is reported. Other aspects of his physical and mental development were within normal limits. The constellation of clinical features in this patient appear to represent a previously undescribed syndrome.

Defective dendritic cell maturation in a child with nucleotide excision repair deficiency and CD4 lymphopenia

We report a case of a combined immunodeficiency (CID) in a child affected by trichothiodystrophy (TTD) characterized by an altered response to ultraviolet (UV) light due to a defect in the XPD gene. The XPD gene encodes a subunit of the transcription factor II H (TFIIH), a complex involved in nucleotide-excision repair (NER) and basal transcription. Our patient showed neurological and immune system abnormalities, including CD4 + lymphopenia never previously reported in TTD patients. In vitro immunological studies revealed a marked reduction in T-cell proliferation in response to mitogens and CD3 cross-linking which was partially recovered by the addition of anti-CD28 antibody or exogenous interleukin-2. The patient's T cells displayed alterations in T-cell receptor (TCR/CD3) proximal signalling characterized by marked reduction in Lck kinase activity coupled with a constitutive hyperactivation of Fyn kinase. Despite these alterations, normal levels of Lck and Fyn proteins were detected. The role of antigen-presenting cells (APCs) in the pathogenesis of the T-cell defect was investigated by analysing dendritic cells (DCs) generated from the patient's blood monocytes. In these cells, flow cytometry revealed significantly reduced expression of the CD86 co-stimulatory molecules and HLA glycoproteins. In addition, the patient's DCs showed a decreased ability to stimulate naive T lymphocytes. Overall, the results of our study suggest that a defective TFIIH complex might result in alterations in T cells and DC functions leading to a severe immunodeficiency.

Acquired hair fragility in pili anulati: causal relationship with androgenetic alopecia

Pili anulati are defined by characteristic alternating light and dark banding in the hair shaft, due to air-filled spaces between the macrofibrillar units of the hair cortex, and are regarded as a congenital hair shaft disorder without increased hair fragility. Two cases of pili anulati are presented, in which fragility of hair developed in a causal relationship with the onset of androgenetic alopecia. Accordingly, trichorrhexis-nodosa-like hair fracturing was exclusively limited to the androgenetic region. In general, secondary trichorrhexis nodosa is an unspecific finding related to excess stress of hair in relation to its fragility. With onset of hair thinning due to androgenetic alopecia, progressive reduction of hair shaft diameter may cause increased fragility in pili anulati. In this case, hair shaft fracturing occurs within the area of androgenetic alopecia and colocalizes with the air-filled cavities of pili anulati.

Trichorhinophalangeal syndrome type I: clinical and molecular characterization of 3 members of a family and 1 sporadic case

BACKGROUND

Trichorhinophalangeal syndrome type I (TRPS I) is a rare autosomal dominant disorder clinically characterized by sparse and slow-growing hair, pear-shaped nose, elongated philtrum, thin upper lip, and bone deformities, in particular, cone-shaped epiphyses of the phalanges. Very recently, the responsible gene TRPS1 has been cloned on human chromosome 8q24.

OBSERVATION

We describe a mother and her 2 daughters and a female patient with a sporadic case of TRPS I. In the familial case, mutation analysis showed an insertional mutation at position 2480 of the TRPS1 gene leading to a premature translational stop. Careful clinical examination showed craniofacial and radiologic features typical of TRPS I, including short stature, in all 3 affected individuals. Additionally, they presented with a receded triangular medio-occipital hairline, which has not been described in TRPS I so far. In the sporadic case, we identified a single base deletion at position 2110 of the TRPS1 gene leading to frameshift and premature translational stop at codon 766. The patient presented with the typical TRPS I phenotype but was of normal stature.

CONCLUSIONS

The TRPS I is characterized by variable clinical expression of the triad of hair, craniofacial, and skeletal abnormalities. New genetic approaches, including mutation analysis, now allow identification of carriers of the TRPS1 gene mutations.

Fibroblast growth factor receptor 2 (Fgfr2) plays an important role in eyelid and skin formation and patterning

Initiating as protruding ridges above and below the optic vesicle, the eyelids of mice grow across the eye and temporarily fuse in fetal life. Mutations of a number of genes disrupt this developmental process and result in a birth defect, "open-eyelids at birth." Here we show that a critical event for eyelid induction occurs at embryonic day 11.5 (E11.5) when the single cell-layered ectoderm in the presumptive eyelid territory increases proliferation and undergoes morphologic transition to form cube-shaped epithelial cells. Using embryos lacking the Fgfr2 Ig domain III (Fgfr2(DeltaIII/DeltaIII)) generated by tetraploid rescue and chimeric embryo formation approaches, we demonstrate that this event is controlled by Fgfr2 signals as the Fgfr2(DeltaIII/DeltaIII) mutation blocks these changes and results in embryos without eyelids. Fgfr2 and its ligands are differentially expressed in the ectoderm and underlying mesenchyme and function in a reciprocal interacting loop that specifies eyelid development. We also demonstrate that similar defects account for failure of skin formation at early stages. Interestingly, Fgfr2-independent skin formation occurs at E14.5 mutant embryos, resulting in much thinner, yet well-differentiated epidermis. Notably, mutant skin remains thin with decreased hair density after transplantation to wild-type recipients. These data demonstrate an essential role of Fgfr2 in eyelid and skin formation and patterning.

Effects of XPD mutations on ultraviolet-induced apoptosis in relation to skin cancer-proneness in repair-deficient syndromes

To understand the relationship between DNA repair, apoptosis, transcription, and cancer-proneness, we have studied the apoptotic response and the recovery of RNA synthesis following ultraviolet C and ultraviolet B irradiation in nucleotide excision repair deficient diploid fibroblasts from the cancer-prone xeroderma pigmentosum (XP) syndrome patients and the non-cancer-prone trichothiodystrophy (TTD) patients. Analysis of four XPD and four TTD/XPD fibroblast strains presenting different mutations on the XPD gene has shown that XPD cells are more sensitive to ultraviolet-induced apoptosis than TTD/XPD cells, and this response seems to be modulated by the type and the location of the mutation on the XPD gene. Moreover, the other xeroderma pigmentosum fibroblast strains analyzed (groups A and C) are more sensitive to undergo apoptosis after ultraviolet irradiation than normal human fibroblasts, showing that the cancer-proneness of xeroderma pigmentosum patients is not due to a deficiency in the ultraviolet-induced apoptotic response. We have also found that cells from transcription-coupled repair deficient XPA, XPD, TTD/XPD, and Cockayne's syndrome patients undergo apoptosis at lower ultraviolet doses than transcription-coupled repair proficient cells (normal human fibroblasts and XPC), indicating that blockage of RNA polymerase II at unrepaired lesions on the transcribed strand is the trigger. Moreover, XPD and XPA cells are more sensitive to ultraviolet-induced apoptosis than trichothiodystrophy and Cockayne's syndrome fibroblasts, suggesting that both cyclobutane pyrimidine dimers and pyrimidine 6-4 pyrimidone on the transcribed strand trigger apoptosis. Finally, we show that apoptosis is directly proportional to the level of inhibition of transcription, which depends on the density of ultraviolet-induced lesions occurring on transcribed sequences.

Genotype-phenotype assessment in autosomal recessive arrhythmogenic right ventricular cardiomyopathy (Naxos disease) caused by a deletion in plakoglobin

OBJECTIVES

The purpose of this study was to examine the genotype-phenotype relation with respect to penetrance, age and severity of expression, disease progression and prognosis in a recessively inherited arrhythmogenic right ventricular cardiomyopathy (ARVC).

BACKGROUND

Naxos disease is a recessively inherited ARVC caused by a mutation in the gene encoding plakoglobin (cell adhesion protein) in which the cardiac phenotype is associated with palmoplantar keratoderma and woolly hair.

METHODS

Twelve families with Naxos disease underwent cardiac and molecular genetic investigation. Serial cardiac assessment with annual resting 12-lead and 24-h ambulatory electrocardiogram (ECG) and two-dimensional echocardiography was performed during 1 to 16 years, median 7 +/- 6 years in all 78 surviving members.

RESULTS

Twenty-eight surviving members were homozygous and 40 were heterozygous for the mutation. All adults who were homozygous (n = 26) fulfilled the diagnostic criteria for ARVC, the youngest by the age of 13 years. In eight who were heterozygous, minor ECG or echocardiographic abnormalities were observed. Of the 26 subjects who were affected homozygotes, 92% showed ECG abnormalities, 92% ventricular arrhythmias, 100% right ventricular structural alterations and 27% left ventricular involvement. During follow-up (10 +/- 6 years), 16 (62%) developed structural progression, 12 (46%) arrhythmic events and 7 (27%) heart failure. The annual disease-related and sudden death mortality was 3% and 2.3%, respectively.

CONCLUSIONS

Autosomal recessive ARVC caused by a mutation in plakoglobin was 100% penetrant by adolescence. Affected subjects who were homozygous experienced progressive disease with adverse prognosis. A minority of subjects who were heterozygous showed minor ECG/echocardiographic changes, but clinically significant disease did not develop.

Pure ectodermal dysplasia: retrospective study of 16 cases and literature review

OBJECTIVE

To review the possible craniomaxillofacial deformative consequences associated with ectodermal dysplasias and embryonic malformations, which include dental ageneses.

SETTING

Oral and Maxillofacial Surgery Department, University Hospital, Lille, France.

PATIENTS

Sixteen patients (seven boys and nine girls, aged 4 to 34 years) with pure ectodermal dysplasia (no ectodermal dysplasia syndromes).

INTERVENTIONS

All patients had a clinical examination. Seven (two boys and five girls, aged 4 to 25 years) had undergone plaster casts and radiographic and Delaire's cephalometric studies before being treated.

MAIN OUTCOME MEASURES

All patients had tooth ageneses (from hypodontia to anodontia), associated with cutaneous dyshidrosis and hair and nail dystrophy. Most of them had a short face, with an unusual facial concavity, a maxillary retrusion, and a relative mandibular protrusion. MANAGEMENT RESULTS AND DISCUSSION: Depending on their ages and their orthopedic abnormalities, patients underwent either dental or prosthodontic, orthodontic, orthopedic, orthognathic, or implant treatment. So as not to interfere with the growth pattern, we preferred to reserve implant and orthognathic surgery for full-grown cases.

CONCLUSIONS

Oral and maxillofacial surgeons must undertake a comprehensive approach to these patients to improve their dental, masticatory, growing, and orthognathic conditions.

Treatment of spinal muscular atrophy by sodium butyrate

Spinal muscular atrophy (SMA) is an autosomal recessive disease characterized by degeneration of the anterior horn cells of the spinal cord, leading to muscular paralysis with muscular atrophy. No effective treatment of this disorder is presently available. Studies of the correlation between disease severity and the amount of survival motor neuron (SMN) protein have shown an inverse relationship. We report that sodium butyrate effectively increases the amount of exon 7-containing SMN protein in SMA lymphoid cell lines by changing the alternative splicing pattern of exon 7 in the SMN2 gene. In vivo, sodium butyrate treatment of SMA-like mice resulted in increased expression of SMN protein in motor neurons of the spinal cord and resulted in significant improvement of SMA clinical symptoms. Oral administration of sodium butyrate to intercrosses of heterozygous pregnant knockout-transgenic SMA-like mice decreased the birth rate of severe types of SMA-like mice, and SMA symptoms were ameliorated for all three types of SMA-like mice. These results suggest that sodium butyrate may be an effective drug for the treatment of human SMA patients.

Hair loss: an overview

Hair loss is a common problem in men and women. Correct diagnosis of hair disorders is complex and requires evaluation of clinical presentation, history, physical examination, and laboratory tests. Hair loss may be categorized as hair shaft abnormalities, permanent alopecia, or nonpermanent alopecia. Nonpermanent alopecia, the most common type, includes androgenetic alopecia, telogen effluvium, alopecia areata, and traction alopecia. The hallmark of this group is the possibility of complete regrowth with adequate treatment.

The spectrum of pathogenic mutations in SPINK5 in 19 families with Netherton syndrome: implications for mutation detection and first case of prenatal diagnosis

The Comèl-Netherton syndrome is an autosomal recessive multisystemic disorder characterized by localized or generalized congenital ichthyosis, hair shaft abnormalities, immune deficiency, and markedly elevated IgE levels. Life-threatening complications during infancy include temperature and electrolyte imbalance, recurrent infections, and failure to thrive. To study the clinical presentations of the Comèl-Netherton syndrome and its molecular cause, we ascertained 19 unrelated families of various ethnic backgrounds. Results of initial linkage studies mapped the Comèl-Netherton syndrome in 12 multiplex families to a 12 cM interval on 5q32, thus confirming genetic homogeneity of Comèl-Netherton syndrome across families of different origins. The Comèl-Netherton syndrome region harbors the SPINK5 gene, which encodes a multidomain serine protease inhibitor (LEKTI) predominantly expressed in epithelial and lymphoid tissues. Recently, recessive mutations in SPINK5 were identified in several Comèl-Netherton syndrome patients from consanguineous families. We used heteroduplex analysis followed by direct DNA sequencing to screen all 33 exons and flanking intronic sequences of SPINK5 in the affected individuals of our cohort. Mutation analysis revealed 17 distinct mutations, 15 of which were novel, segregating in 14 Comèl-Netherton syndrome families. The nucleotide changes included four non-sense mutations, eight small deletions or insertions leading to frameshift, and five splice site defects, all of which are expected to result in premature terminated or altered translation of SPINK5. Almost half of the mutations clustered between exons 2 and 8, including two recurrent mutations. Genotype-phenotype correlations suggested that homozygous nucleotide changes resulting in early truncation of LEKT1 are associated with a severe phenotype. For the first time, we used molecular data to perform prenatal testing, thus demonstrating the feasibility of molecular diagnosis in the Comèl-Netherton syndrome.

Clinico-immunological heterogeneity in Comèl-Netherton syndrome

BACKGROUND

Comèl-Netherton syndrome (CN) is characterized by atopic-eczema-like skin abnormalities combined with linear ichthyotic lesions, hair shaft abnormalities and atopy with high IgE levels.

OBJECTIVE

Five children with CN are described. In 2 of the 3 CN patients still alive, analysis of cytokines regulating IgE synthesis was performed.

METHODS

In peripheral blood mononuclear cells and cultures of purified T cells, mRNA expression and protein production of interleukin 4 (IL-4), IL-13, IL-5 and interferon gamma were analysed. The results were compared with the values in age-matched atopic dermatitis patients and healthy children.

RESULTS

The 5 CN patients showed striking differences in disease severity and evolution. Marked differences were found in several cytokines in the 2 analysed CN patients. Low percentages of natural killer cells were observed in both CN patients.

CONCLUSION

The regulation of IgE production in patients with CN is varied and complex. The CN patients were heterogeneous in terms of Th2 skewing.

Oligodontia is associated with extra-oral ectodermal symptoms and low whole salivary flow rates

INTRODUCTION

Ectodermal dysplasias (EDs) involve abnormal development of hair, teeth, nails, and sweat glands.

OBJECTIVES

(1) To investigate the frequency of extraoral ectodermal symptoms in persons with oligodontia (>6 congenitally missing teeth). (2) To examine whole salivary flow rates in oligodontia patients, with special emphasis on persons with EDs. SURVEY GROUP AND METHODS: Sixty-eight persons with oligodontia and 39 healthy control persons were included. All participants underwent an interview, general and oral examinations, and whole salivary secretory tests.

RESULTS

Thirty-nine (57%) of the oligodontia patients had disturbances in either hair, nails and/or sweat production in addition to teeth and were classified as the ED group. The remaining 29 oligodontia patients had no obvious signs of EDs (non-ED group). The prevalences of dry skin, asthma and eczema were higher, and whole salivary secretory rates lower, in the ED group as compared to the control group. Intermediate values were observed in the non-ED group. Incisors, canines and molars were more frequently missing in the ED group than in the non-ED group, whereas no differences were observed in the frequency of missing premolars. Negative correlations between the number of missing teeth and unstimulated and chewing stimulated whole salivary secretory rates were found.

Cranioectodermal dysplasia: a new patient with an inapparent, subtle phenotype

Cranioectodermal dysplasia is a rare syndrome characterized by craniofacial and skeletal anomalies and ectodermal dysplasia. Life-threatening associated conditions (i.e., kidney failure and abnormal regulation of the parathyroid-bone axis) can also develop. We report a patient whose features are suggestive of an inapparent, subtle phenotype of the syndrome. The patient is a 4-year-old girl with only dolichocephaly and clinodactyly; microdontia, hypodontia, and taurodontia (i.e., cone-shaped teeth); anteverted nares, full cheeks, and everted lower lip; epicanthal folds, hypertelorism and hyperopia; and corpus callosum hypoplasia. She has no rhizomelic limb shortening or hair abnormalities. In view of the rarity of the cranioectodermal dysplasias, the variability of the phenotype, and the uncertain outcome of some previously described patients, we believe this inapparent, subtle case should reported to enable better understanding and treatment of this rare syndrome.

Woolly hair, premature loss of teeth, nail dystrophy, acral hyperkeratosis and facial abnormalities: possible new syndrome in a Dutch kindred

We describe a Dutch kindred with a possibly novel dominant syndrome of premature loss of curly, brittle hair, premature loss of teeth due to caries, nail dystrophy and acral keratoderma. We discuss the possibility that this ectodermal dysplasia of group 1-2-3-4 is a variant of known disorders such as pachyonychia congenita. We conclude that none of these diagnoses fits the symptoms we observe in our patients and propose the name curly hair-acral keratoderma-caries syndrome in view of the most obvious abnormalities.

A case of Netherton's syndrome with cerebral infarction

Netherton's syndrome, a rare congenital disease of childhood, is characterized by variable cutaneous erythematous eruptions with different manifestations. A five-year-old boy, who presented with ichthyosis linearis circumflexa, atopic manifestations and pili torti, had spastic hemiparesia due to cerebral infarction. Netherton's syndrome can easily be misdiagnosed as Leiner's disease, generalized psoriasis or nonbullous congenital ichthyosiform erythroderma, especially in the neonatal period, because of its nonspecific clinical and histological features. Pediatricians should consider this syndrome in the differential diagnosis of the generalized erythematous skin disorders of childhood associated with various abnormalities.

Trichothiodystrophy: update on the sulfur-deficient brittle hair syndromes

Trichothiodystrophy (TTD) refers to a heterogeneous group of autosomal recessive disorders that share the distinctive features of short, brittle hair and an abnormally low sulfur content. Within the spectrum of the TTD syndromes are numerous interrelated neuroectodermal disorders. The TTD syndromes show defective synthesis of high-sulfur matrix proteins. Abnormalities in excision repair of ultraviolet (UV)-damaged DNA are recognized in about half of the patients. Three distinct autosomal recessive syndromes are associated with nucleotide excision repair (NER) defects: the photosensitive form of TTD, xeroderma pigmentosum, and Cockayne syndrome. The unifying feature of these conditions is exaggerated sensitivity to sunlight and UV radiation. In contrast to patients with xeroderma pigmentosum, no increase of skin cancers in patients with TTD has been observed. Genetically, 3 complementation groups have been characterized among photosensitive patients with TTD. Most patients exhibit mutations on the two alleles of the XPD gene. Rarely, mutated XPB gene or an unidentified TTD-A gene may result in TTD. In UV-sensitive TTD, the TFIIH transcription factor containing XPB and XPD helicase activities necessary for both transcription initiation and DNA repair is damaged. Beyond deficiency in the NER pathway, it is hypothesized that basal transcription may be altered leading to decreased transcription of specific genes. Depressed RNA synthesis may account for some clinical features, such as growth retardation, neurologic abnormalities, and brittle hair and nails. Therefore the attenuated expression of some proteins in differentiated cells is most likely explained by a mechanism distinct from DNA repair deficiency. The first transgenic mouse models for NER deficiencies have been generated. The TTD mouse as well as related cell models will provide important tools to understand the complex relationships between defects in DNA repair, low-sulfur hair shaft disorders, and the genotype-phenotype correlates for this constellation of inherited disorders, including the lack of predisposition to cancer in patients with TTD.

Abnormal differentiation of epidermis in transgenic mice constitutively expressing cyclooxygenase-2 in skin

In prostanoid biosynthesis, the first two steps are catalyzed by cyclooxygenases (COX). In mice and humans, deregulated expression of COX-2, but not of COX-1, is characteristic of epithelial tumors, including squamous cell carcinomas of skin. To explore the function of COX-2 in epidermis, a keratin 5 promoter was used to direct COX-2 expression to the basal cells of interfollicular epidermis and the pilosebaceous appendage of transgenic mouse skin. COX-2 overexpression in the expected locations, resulting in increased prostaglandin levels in epidermis and plasma, correlated with a pronounced skin phenotype. Heterozygous transgenic mice exhibited a reduced hair follicle density. Moreover, postnatally hair follicle morphogenesis and thinning of interfollicular dorsal epidermis were delayed. Adult transgenics showed a body-site-dependent sparse coat of greasy hair, the latter caused by sebaceous gland hyperplasia and increased epicutaneous sebum levels. In tail skin, hyperplasia of scale epidermis reflecting an increased number of viable and cornified cell layers was observed. Hyperplasia was a result of a disturbed program of epidermal differentiation rather than an increased proliferation rate, as reflected by the strong suppression of keratin 10, involucrin, and loricrin expression in suprabasal cells. Further pathological signs were loss of cell polarity, mainly of basal keratinocytes, epidermal invaginations into the dermis, and formation of horn perls. Invaginating hyperplastic lobes were surrounded by CD31-positive vessels. These results demonstrate a causal relationship between transgenic COX-2 expression in basal keratinocytes and epidermal hyperplasia as well as dysplastic features at discrete body sites.

Craniofacial characteristics of Klippel-Feil syndrome in an eight year old female

A female eight year, one month old patient with Klippel-Feil syndrome has been introduced. General appearance of the patient was characterized by short neck with limited head movements, craniofacial asymmetry, low posterior hairline and a short stature. Cephalometric analysis revealed a Class I dentoskeletal pattern with an excessive mandibular plane angle and fused cervical vertebrae. Panoramic radiogram showed congenitally missing lower second premolars and right central incisor.

New syndrome characterized by sparse hair, prominent nose, small mouth, micrognathia, cleft palate, crumpled upper helices, digit anomaly, and mild developmental delay

A brother and a sister show very similar clinical features, including sparse hair in the first year of life, prominent nose, small mouth, micrognathia, high arched palate or cleft palate, crumpled upper helices, flexion limitation of the distal interphalangeal joint of the fingers, and mild developmental delay. Their clinical appearance suggests a premature aging phenotype, but is not really compatible with the hitherto known syndromes of that group. The mode of inheritance is likely autosomal recessive.

Hirschsprung disease associated with severe cartilage-hair hypoplasia

Cartilage-hair hypoplasia is a chondrodysplasia with a high incidence of Hirschsprung disease. This study suggests that Hirschsprung disease is associated especially with severe cartilage-hair hypoplasia: the patients with Hirschsprung disease had severe growth failure and a higher incidence of alopecia, infections, malignancies, and childhood anemia than the patients with cartilage-hair hypoplasia who did not have Hirschsprung disease.

A high frequency of XO offspring from X(Paf)Y* male mice: evidence that the Paf mutation involves an inversion spanning the X PAR boundary

It has previously been reported that 19% of the daughters of males carrying the X-linked mutation patchy fur (Paf) are XO with a maternally derived X chromosome. We now report that hemizygous Paf males that also carry the variant Y chromosome Y*, show a much increased XO production ( approximately 40% of daughters). We hypothesize that the Paf mutation is associated with an inversion spanning the pseudoautosomal region (PAR) boundary, and that this leads to preferential crossing over between the resulting inverted region of PAR and an equivalent inverted PAR region within the compound Y* PAR. This would lead to the production of dicentric X and acentric Y products and consequent sex chromosome loss. This interpretation is supported by analysis of the sex chromosome complements at the second meiotic metaphase, which revealed a high incidence of dicentrics. Another curious feature of the Paf mutation is that mice that are homozygous Paf have more hair than mice that are hemizygous Paf. This can be explained if the Paf mutation is a hypomorphic mutation that escapes X inactivation because, unlike the wild type allele, it is now located within the PAR.