A novel isoform of human lymphoid enhancer-binding factor-1 (LEF-1) gene transcript encodes a protein devoid of HMG domain and nuclear localization signal.

Lymphoid enhancer-binding factor-1 (LEF-1), a member of the high mobility group (HMG) family of proteins, regulates expression of T-cell receptor-alpha gene and is one of the key regulatory molecules in the epithelial-mesenchymal interactions during embryonic development. Among others, LEF-1 regulates expression of cytokeratin genes involved in formation of hair follicles and the gene encoding the cell-adhesion molecule E-cadherin. Transcription factor LEF-1, which acts as a dimer, binds beta-catenin and is involved in signal transduction by the wnt pathway. We have cloned and sequenced a novel isoform of human LEF-1 gene transcript. This isoform encodes a truncated protein devoid of HMG domain and nuclear localization signal but retaining beta-catenin binding domain. This isoform might either act in a dominant-negative manner by interfering with native LEF-1, or might bind beta-catenin in the cytosol, which would result in attenuation of the signals transmitted by the LEF-beta-catenin pathway.

Mutations in the EDA gene in three unrelated families reveal no apparent correlation between phenotype and genotype in the patients with an X-linked anhidrotic ectodermal dysplasia.

Anhidrotic ectodermal dysplasia (EDA) is caused by mutations in the EDA gene encoding ectodysplasin A, a member of the TNF ligand superfamily involved in the communication between the cells. The structure of the EDA gene was investigated in three patients exhibiting clinical symptoms of EDA in an attempt to correlate the molecular findings with the phenotype of the patients. Genomic DNA was analyzed by single stranded conformation polymorphism (SSCP) followed by direct sequencing. In one of the patients, as well as in his heterozygous mother and sister, a single T insertion was evidenced in exon 3 between nucleotides 713 and 714 that changed Lys codon (AAA) into a termination codon TAA (Lys158Ter). In the other patient, A1321T transversion was demonstrated. The same mutation was found in his heterozygous mother and resulted in a change of Ileu360Asn that might generate an additional glycosylation site. In the third patient an A1285G transition was revealed. This mutation that originated de novo was localized in a region that is highly conserved in TNF ligand family and caused substitution of Ala349Thr. Localization of the mutations in the extracellular domain of ectodysplasin A suggested that the primary cause of EDA is a defect in communication between the cells responsible for the development of skin appendages. Despite a different character and localization of the mutations, no apparent correlation between phenotype and genotype of the patients was evidenced. Some differences in the patients' phenotype were observed.

Sequence polymorphisms of the EDA and the DL genes in the patients with an X-linked and an autosomal forms of anhidrotic ectodermal dysplasia.

Oligodontia, sparse hair and deficiency of eccrine sweat glands are the features characteristic for the phenotype of the patients with anhidrotic ectodermal dysplasia (EDA). This syndrome is caused by mutations in the EDA or DL (downless) genes, encoding members of the TNF ligand and TNF receptor families, involved in the communication between the cells during embryonic life. We investigated both the coding and noncoding regions of the EDA and the DL genes in the patients exhibiting clinical symptoms of ectodermal dysplasia. Sequence analysis of the amplified fragments of the EDA gene revealed polymorphisms in introns three, four and five. The polymorphism in intron four was found in about 60% of the patients and was no more frequent than in the normal individuals. The two other polymorphisms were rare. Polymorphisms were also observed in exons 9 and 12 of the DL gene, but they did not alter the sequence of the protein product of the gene. Our results indicate that in order to accelerate screening for the mutations of the EDA gene and reduce the costs, the amplified fragments should not contain intronic sequences. However, in the case of the DL gene, where polymorphic sites are located in exons, restriction analysis with the use of appropriate enzyme should be conducted, but usually sequencing analysis could not be avoided.

The novel polymorphic variants within the paired box of the PAX9 gene are associated with selective tooth agenesis.

It has been reported that two genes MSX1 and PAX9, which encode transcription factors, are associated with selective tooth agenesis. Expression of these genes specifically marks the regions of the mesenchyme where the tooth buds are formed. A mutation in the MSX1 gene, detected in a single family, resulting in an Arg-->Pro substitution in the homeodomain of the protein product of this gene has previously been associated with the deficiency of second premolars and third molars. However, mutations of the MSX1 gene were excluded in the patients with agenesis of the other type of teeth. In a single family with the lack of first and second molars, a mutation in the PAX9 gene was found. In our group of patients with the deficiency of various teeth, in 20% of the patients and their relatives sequence analysis revealed a C-->T transition in the coding sequence of the PAX9 gene. However, this polymorphism does not alter amino acid sequence of the protein product of this gene.

Cloning of the lymphoid enhancer binding factor-1 (Lef-1) cDNA from rat kidney: homology to the mouse sequence.

We have cloned and sequenced rat cDNA that encodes the Lef-1 protein. The cDNA, containing 1194 nt exhibits 94% similarity to the mouse Lef-1 cDNA. The deduced amino-acids sequence of rat Lef-1 protein, consisting of 397 amino acids, exhibited 98% homology with the known sequence of mouse Lef-1 protein.

Mutation in the regulatory region of the EDA gene coincides with the symptoms of anhidrotic ectodermal dysplasia.

We have investigated a fragment of the regulatory region of the EDA gene in a patient with clinical symptoms of anhidrotic ectodermal dysplasia (EDA), whose DNA sequence of exon 1 was normal. The single-strand conformation polymorphism (SSCP) analysis of PCR-amplified fragments of the regulatory region of the EDA gene suggested a mutation localized within the fragment extending from nucleotide -571 to -182 upstream of the 5' end of the cDNA. Sequence analysis of this fragment documented an additional adenine in position -452, located 32 nucleotides upstream from the response element HK-1, a target for transcription factor LEF-1, involved in the differentiation of tissues of ectodermal and mesodermal origin. We postulate that this mutation might interfere with the transcription process of the EDA gene and might be responsible, at least in part, for the clinical symptoms of anhidrotic ectodermal dysplasia.