Genetic variations of HLA-DRB1 and susceptibility to Kawasaki disease in Taiwanese children.

Although some previous studies have reported that genetic and immunologic factors play important roles in the pathogenesis of Kawasaki disease (KD), the etiologic factors of this enigmatic pediatric disease are still poorly understood. The purpose of this study was to investigate whether polymorphisms of the human leukocyte antigen DRB1 (HLA-DRB1) gene are associated with KD and the development of coronary artery lesions (CAL) in Taiwanese children. Genomic DNA was extracted from whole blood samples from 145 children with KD and 331 healthy controls. The HLA-DRB1 gene was genotyped by polymerase chain reaction (PCR) and sequence-based typing assays. We found that the distribution of HLA-DRB1 allele families and alleles in children with KD did not differ from that in healthy controls. Stratified analysis did not demonstrate any association between particular HLA-DRB1 allele families or alleles and the development of CAL in children with KD. These findings suggest that susceptibility to KD and CAL is not associated with the HLA-DRB1 gene in a Taiwanese population. If immunogenetic determinants are involved in this disease and its complications in Taiwanese children, they must involve genes other than HLA-DRB1.

Different modes of regulation of transcription and pre-mRNA processing of the structurally juxtaposed homologs, Rnf33 and Rnf35, in eggs and in pre-implantation embryos.

Molecular events involved in gene expression in unfertilized eggs and pre-implantation embryos are beginning to be understood. In this work, we investigated the transcription and processing of two structurally juxtaposed mouse RING finger protein genes, Rnf33 and Rnf35. Transcripts of these genes are detected only in eggs and in pre-implantation embryos. Both genes are intronless except for a solitary intron in the 5'-untranslated region. Here, we showed by rapid amplification of cDNA ends (RACE) and reverse transcription experiments that Rnf35 transcription uses a single promoter and a terminating site. On the other hand, Rnf33 is transcribed using multiple promoters. At the four-cell stage, however, Rnf33 mRNA with a single transcription start site derived from the proximal promoter is detected, indicating that it is the major promoter. Sequences upstream of the Rnf35 and the major Rnf33 transcription start sites carry no TATA boxes but a putative transcription initiator (Inr) element is discernible in each case. The processing of the 3'-end of the Rnf33 mRNA is also in disarray with multiple 3'-ends, an event that may be related to the absence of the AAUAAA element and the utilization of AAUAAA-like proxies. The multiplicity of the 3'-untranslated region is partially amended at the four-cell stage when only two major 3'-ends are in use. This work demonstrates that expression of some maternal and early zygotic genes may be opportunistic until a stringent transcriptional regulation mechanism is imposed.

Display of different modes of transcription by the promoters of an early embryonic gene, Zfp352, in preimplantation embryos and in somatic cells.

We have previously reported a Krupple-like finger protein gene, Zfp352, which is expressed temporarily in two- to eight-cell mouse embryos. The Zfp352 gene is intron-less in the coding region but carries a solitary 4.3-kb intron in the 5'-untranslated region. In this study, we have analyzed the Zfp352 promoter activity in early embryos and in somatic cells. We determined that the major Zfp352 promoter, designated P1 and located upstream of exon 1, is utilized in both early embryos and in somatic cells. A TATA-like box and a transcription initiator element are discernible in the P1 promoter. We uncovered an alternative promoter, designated P2, in the intron. 5'-Rapid amplification of cDNA ends and real-time RT-PCR experiments indicated that the P2 promoter is weak and is probably fortuitous in early embryos. In somatic cells, however, transfection experiments showed that P2 is as active as P1 as a promoter. Furthermore, P2 appears to be composed of two different subdomains used differentially for transcription initiation in embryos and in somatic cells. Our observations may bear relevance in explaining developmental deficiencies associated with somatic cell cloning experiments.

Generation of two homologous and intronless zinc-finger protein genes, zfp352 and zfp353, with different expression patterns by retrotransposition.

We have previously reported a mouse zinc-finger protein gene, Zfp352 (formerly 2czf48), that is expressed in early mouse embryos. Here, we report the genomic structure of Zfp352 and its lung-specific homolog, Zfp353. The two genes map on different chromosomes at 4C6 and 8B3.1. Both genes are intronless, except for the presence of a single 4.6-kb intron in the 5' untranslated region of Zfp352. The genes use different RNA start sites located 1.2 kb apart within the 5' homologous region. LINE1 sequences are structurally associated with the genes and form an integral part of Zfp353 transcripts, suggesting previous retrotransposition events. We propose a model of evolution of the genes. The main feature of the model is the presence of a fortuitous upstream promoter and an intron in the first retrotransposition site, creating a pre-Zfp352 gene with a 5' untranslated region intron. A second retrotransposition event copying from the pre-Zfp352 retroposon and removing the fortuitous intron resulted in the intronless Zfp353 at a different chromosomal location and with a different mode of expression. The model may be applicable to other genes with a similar structure with a single intron in the 5' untranslated region. The exact role of LINE1 in the retrotransposition events remains to be elucidated.

Use of a common promoter by two juxtaposed and intronless mouse early embryonic genes, Rnf33 and Rnf35: implications in zygotic gene expression.

Rnf33 and Rnf35 are mouse RING finger protein genes that are transcribed temporally in the preimplantation mouse embryo, predominantly at the two-cell embryonic stage. The genes are juxtaposed in a 20-kb genomic region and are both intronless except for a single intron in the 5' untranslated region (5'-UTR). Based on analysis of the Rnf33/35 genomic sequence and cDNA sequences derived by in silico mining, we found that the Rnf33 and Rnf35 mRNAs are apparently transcribed from the same putative promoter and may be products of alternative splicing of the same pre-mRNA generated through differential 3' cleavage and polyadenylation. We also detected a second variant of Rnf35 in two-cell embryo generated through a second splicing event using an unconventional 5' splice junction. Our observations on the mode of transcription of Rnf33 and Rnf35 are consistent with the hypothesis that transcription of zygotic genes is promiscuous, and that the solo 5'-UTR intron may serve to facilitate efficient translation.