Analysis of the p63 gene in classical EEC syndrome, related syndromes, and non-syndromic orofacial clefts.

EEC syndrome is an autosomal dominant disorder with the cardinal signs of ectrodactyly, ectodermal dysplasia, and orofacial clefts. EEC syndrome has been linked to chromosome 3q27 and heterozygous p63 mutations were detected in unrelated EEC families. In addition, homozygous p63 null mice exhibit craniofacial abnormalities, limb truncations, and absence of epidermal appendages, such as hair follicles and tooth primordia. In this study, we screened 39 syndromic patients, including four with EEC syndrome, five with syndromes closely related to EEC syndrome, and 30 with other syndromic orofacial clefts and/or limb anomalies. We identified heterozygous p63 mutations in three unrelated cases of EEC syndrome, two Iowa white families and one sporadic case in a Filipino boy. One family is atypical for EEC and has features consistent with Hay-Wells syndrome. In this family, the mutation ablates a splice acceptor site and, in the other two, mutations produce amino acid substitutions, R280C and R304Q, which alter conserved DNA binding sites. Germline mosaicism was detected in the founder of the mutation in one case. These three cases show significant interfamilial and intrafamilial variability in expressivity. We also screened p63 in 62 patients with non-syndromic orofacial clefts, identifying an intronic single nucleotide polymorphism but finding no evidence of mutations that would explain even a subset of non-syndromic orofacial clefts. This study supports a common role for p63 in classical EEC syndrome, both familial and sporadic, but not in other related or non-syndromic forms of orofacial clefts.

SCNN1, an epithelial cell sodium channel gene in the conserved linkage group on mouse chromosome 6 and human chromosome 12.

SCNN1, a gene encoding a nonvoltage-gated sodium channel, was detected using a rat colon cDNA probe with homology to Caenorhabditis elegans degenerin genes. Human SCNN1 was assigned to chromosome 12 using the NIGMS hybrid mapping panel 2. Mouse SCNN1 was mapped to a conserved linkage group on distal chromosome 6. The observed order of mouse genes was centromere-Raf1-(2.1 +/- 2.1)-Scnn1, Vwf-(1.9 +/- 1.9)-Ntf3, with 0/101 recombinants between Scnn1 and Vwf. No rearrangements of genomic DNA were detected in the linked mouse mutations deaf waddler (dfw) and opisthotonus (opt).

Kidney and retinal defects (Krd), a transgene-induced mutation with a deletion of mouse chromosome 19 that includes the Pax2 locus.

The semidominant mutation Krd (kidney and retinal defects) was identified in transgenic line Tg8052. Krd/+ mice have a high incidence of kidney defects including aplastic, hypoplastic, and cystic kidneys. Retinal defects in Krd/+ mice include abnormal electroretinograms and a reduction of cell numbers that is most extreme in the inner cell and ganglion layers. Viability of Krd/+ mice is strongly influenced by genetic background, and growth retardation is observed in young animals. Homozygosity results in early embryonic lethality. Fluorescence in situ hybridization of a transgene-specific probe localized the insertion site to the distal region of mouse Chromosome 19. The sequence of the insertion site revealed transgene insertion into a LINE element with deletion of a single nucleotide from the 3' terminus of the transgene. A polymorphic microsatellite, D19Umi1, was identified in a junction clone and mapped in several large crosses. D19Umi1 is located 1.7 +/- 1.0 cM distal to Pax2, which encodes a paired type transcription factor expressed in embryonic kidney and eye. Deletion of Pax2 from the transgenic chromosome was demonstrated by Southern analysis of genomic DNA from (Krd/+ x SPRET/Ei)F1 mice. Additional genetic and molecular data are consistent with an approximately 7-cM deletion that includes the loci stearoyl CoA desaturase (Scd1), pale ear (ep), D19Mit17, D19Mit24, D19Mit27, D19Mit11, and Pax2. This deletion, Del(19)TgN8052Mm, will be useful for genetic and functional studies of this region of mouse Chromosome 19.

Molecular characterization of a novel human gene, SEC13R, related to the yeast secretory pathway gene SEC13, and mapping to a conserved linkage group on human chromosome 3p24-p25 and mouse chromosome 6.

We previously described sequence tags from 58 novel directionally cloned human cDNAs from an enriched retinal pigment epithelial cell line library (Gieser and Swaroop, 1992). The nucleotide sequence of one of the cDNA clones, AA35 (D3S1231E), showed strong homology to the yeast SEC13 gene, required for vesicle biogenesis from endoplasmic reticulum during the transport of proteins. We have designated the human gene SEC13R (SEC13-Related). The amino acid sequence of the SEC13R gene product shows 70% similarity to yeast Sec13p, suggesting that SEC13R may be the human homolog of SEC13. The deduced polypeptide sequence contains several beta-transducin like 'WD40' repeats, and is rich in serine and threonine residues. The 1.4 kb transcript of SEC13R is detected by Northern analysis in many human tissues. However, RT-PCR analysis using two primer sets from different regions of the gene suggests differential expression of alternately spliced transcripts in various tissues. Somatic cell hybrid and in situ hybridization studies localized the SEC13R gene to human chromosome 3p24-p25. A related sequence was mapped to chromosome 18q11.2-q12. SEC13R was physically mapped to a yeast artificial chromosome (YAC) clone spanning the D3S720 marker from the region of the Von Hippel-Lindau disease locus. The mouse Sec13r gene was mapped to the conserved linkage group on chromosome 6 that corresponds to human chromosome 3p24-p25.

Conserved linkage of early growth response 4, annexin 4, and transforming growth factor alpha on mouse chromosome 6.

The mouse genes encoding early growth response 4 (Egr4), annexin IV (Anx4), and transforming growth factor alpha (Tgfa) have been mapped to a linkage group on mouse chromosome 6 that is conserved on human chromosome 2p11-p13. The genes are closely linked, with 0/215 recombinants between Anx4 and Tgfa and 1/215 recombinants between these genes and Egr4. The genes are located approximately 2 cM distal to mnd2, a mouse mutation causing neuromuscular disease. The results demonstrate that mnd2 is located at an internal position within this conserved linkage group.