Molecular basis of complete C4 deficiency. A study of three patients.

The highly polymorphic fourth component of human complement (C4) is usually encoded by two genes, C4A and C4B, adjacent to the 21-hydroxylase (21-OH) genes and is also remarkable by the high frequency of the null alleles, C4A*Q0 and C4B*Q0. Complete C4 deficiency is exceptional because this condition appears only in homozygotes for the very rare double-null haplotype C4AQ0,BQ0. This condition in most cases gives rise to systemic lupus erythematosus and an increased susceptibility to infections. The molecular basis for complete C4 deficiency has not yet been established. Therefore we studied the DNA of three previously described C4 deficient patients belonging to unrelated families by restriction fragment length polymorphism analysis using C4 and 21-OH probes. These studies revealed a deletion of the C4B and 21-OHA genes in two patients and no deletion at all in the third patient. Therefore, complete C4 deficiency as a result of homozygosity for the C4AQ0, BQ0 haplotype is not a consequence of a deletion of the C4 genes. The molecular basis of this genetic abnormality is certainly very complex and may vary also from one case to another.

Plastid microsatellites for the study of genetic variability in the widespread Cephalanthera longifolia, C. damasonium and C. rubra (Neottieae, Orchidaceae), and cross-amplification in other Cephalanthera species

Plastid microsatellite loci developed for Cephalanthera longifolia were used to examine the level of genetic variation within and between populations of the three widespread Cephalanthera species (C. damasonium, C. longifolia and C. rubra). The most detailed sampling was in C. longifolia (42 localities from Ireland to China; 147 individuals). Eight haplotypes were detected. One was detected in the vast majority of individuals and occurred from Ireland to Iran. Three others were only found in Europe (Ireland to Italy, England to Italy and Austria to Croatia). Two were only found in the Middle East and two only in Asia. In C. damasonium, 21 individuals from 10 populations (England to Turkey) were sampled. Only one haplotype was detected. In C. rubra, 34 individuals from eight populations (England to Turkey) were sampled. Although it was not possible to amplify all loci for all samples of this species, nine haplotypes were detected. Short alleles for the trnS-trnG region found in two populations of C. rubra were characterized by sequencing and were caused by deletions of 26 and 30 base pairs. At this level of sampling, it appears that C. rubra shows the greatest genetic variability. Cephalanthera longifolia, C. rubra and C. damasonium have previously been characterized as outbreeding, outbreeding with facultative vegetative reproduction and inbreeding, respectively. Patterns of genetic variation here are discussed in the light of these reproductive system differences. The primers used in these three species of Cephalanthera were also demonstrated to amplify these loci in another five species (C. austiniae, C. calcarata, C. epipactoides, C. falcata and C. yunnanensis). Although it is sometimes treated as a synonym of C. damasonium, the single sample of C. yunnanensis from China had a markedly different haplotype from that found in C. damasonium. All three loci were successfully amplified in two achlorophyllous, myco-heterotrophic species, C. austinae and C. calcarata. © 2010 The Linnean Society of London.