DNA polymorphism of human HLA-linked complement C4 allotypes, including C4 null alleles, in the Finnish population

Human HLA-linked complement C4 gene products, C4A and C4B, show extensive genetic polymorphism. In both loci, an allele without a gene product, C4 null, is also observed. We have performed a restriction enzyme analysis of genomic DNA samples from individuals having all common (frequency over 1%) C4 protein allotypes observed in the Finnish population. Only one allotype-specific RFLP marker was observed. With some enzymes a DNA polymorphism was observed, which was not detectable by C4 protein typing. Analysis of 10 different C4B null haplotypes and 4 C4A null haplotypes suggested that only one haplotype, HLA-B8 C4A0 B1, carried a C4A gene deletion. This was observed in all 4 unrelated individuals homozygous for this haplotype.     

Types I and IV collagenolytic and plasminogen activator activities in preovulatory ovarian follicles

During ovulation, enzymatic degradation of the extracellular matrix occurs within and around the graafian follicles. In this study, the activities of several different proteolytic enzymes were measured in the culture media of follicles taken from pregnant mare serum gonadotropin (PMSG)-primed immature rats. At 52 h after PMSG, the follicles were cultured for 2 to 15 h in media with or without human chorionic gonadotropin (hCG). Type I collagenase activity in hCG-stimulated follicles gradually increased within 6 h to 3.3-fold above that of the controls. Relatively pure populations of granulosa cells produced type I collagenase to a similar extent. Likewise, type IV collagenase increased 3.8-fold by 6 h after exposure of the follicles to hCG. In contrast, plasminogen activator activity increased by 3.9-fold at 2 h after hCG, but was negligible at 4, 6, and 15 h after incubation. These results suggest that plasminogen activator may activate both type I and type IV collagenase in hCG-stimulated ovulatory follicles.     

Marfan syndrome: exclusion of genetic linkage to five genes coding for connective tissue components in the long arm of chromosome 2

Summary Marfan syndrome represents a heterogeneous connective tissue disease, the symptoms arising in several tissues and organs. The defective gene(s) behind this autosomal dominant condition has not been found despite considerable research. The main targets of the research have been the genes coding for connective tissue components. Several of the candidate genes suspected to be defective in Marfan syndrome are located on the long arm of chromosome 2. These genes include a cluster of two genes coding for fibrillar collagens COL3A1 and COL5A2, and a third member of the collagen gene family: COL6A3. Furthermore, genes for elastin (ELN) and fibronectin (FN) are also located in this area of chromosome 2. We studied this chromosomal area using restriction fragment length polymorphism (RFLP) linkage analysis in five Finnish Marfan families with affected members in three generations. In two point linkage analyses, Lod scores of –3.192 ( = 0.1) to COL3A1, –1.683 ( = 0) to COL6A3 and –2.664 ( = 0.01) to FN were obtained, whereas the linkage analysis between elastin and the disease was non-informative (Lod score 0.444, = 0). With the multipoint linkage analysis that permits simultaneous examination of several loci and more efficient use of family data, we obtained an exclusion of all these loci as the site of the mutation leading to Marfan syndrome in these families.     

Infantile neuronal ceroid-lipofuscinosis is not an allelic form of Batten disease: exclusion of chromosome 16 region with linkage analyses

Infantile neuronal ceroid-lipofuscinosis (CLN1) is the form of neuronal ceroid-lipofuscinoses (NCL) with the earliest onset of symptoms. The locus of the most common form of these disorders, juvenile NCL (CLN3), has been mapped to chromosome 16. We report here linkage data of the same region in Finnish CLN1 families. Our results indicate that CLN1 is not allelic with CLN3 but represents a different locus, which is not located within about 70 cM in chromosome 16.     

Huntington disease in Finland: a molecular and genealogical study

Summary Huntington disease (HD) is found at exceptionally low frequency in the Finnish population. In this population, linkage disequilibrium was earlier established with markers from the D4S10 and D4S43 loci. We now report a continuation to the restriction fragment length polymorphism haplotype analysis, in combination with a genealogical study of all the Finnish HD families. When the HD pedigrees were systematically traced to the 18th century, only one consanguinity was found, and a high percentage (28%) of the families had foreign ancestors. The majority of the Finnish ancestors were localized to border regions or trade centers of the country following the old postal routes. The observed high risk haplotypes formed with markers from the D4S10 and D4S43 loci were evenly distributed among the HD families in different geographical locations. Consequently, the HD gene(s) has most probably arrived in Finland on several occasions via foreign immigrants during the last few centuries.     

Confirmation of the chromosomal localization of human lamp genes and their exclusion as candidate genes for Salla disease

Summary Salla disease is an inherited lysosomal storage disorder caused by accumulation of free sialic acid in the lysosomes. Lamp genes, lamp A and lamp B (lysosome associated membrane proteins), are the first known genes encoding for human lysosomal membrane proteins. Absence of linkage in a large group of families shows that lamp genes are not involved in Salla disease. The lamp genes were localized, using Southern hybridization in hamster — human hybrid cell panels, to chromosomes 13 (lamp A) and X (lamp B).     

Polymorphic restriction sites of type II collagen gene: their location and frequencies in the Finnish population

Restriction fragment length polymorphism (RFLP) of the cartilage-specific type II collagen gene has been studied in the Finnish population. Two high-frequency alleles, also reported in other populations, were detected. The HindIII allele had a frequency of 0.33, and that detected with PvuII a frequency of 0.46. Both of these frequencies resembled the ones reported for other populations. Also one BamHI allele, not earlier reported, was found at a low frequency. Two other previously reported polymorphisms for BamHI and EcoRI were not detected in the Finnish population. The RFLPs showed a fair agreement with the Hardy-Weinberg equilibrium. A linkage disequilibrium was found between PvuII and HindIII markers. The alpha 1(II) collagen gene seems to be more conserved in populations of various origins than the alpha 2(I) collagen gene. These polymorphic collagen markers would be useful in linkage studies of various inherited cartilage disorders.     

Alterations in copper and collagen metabolism in the Menkes syndrome and a new subtype of the Ehlers-Danlos syndrome

Cultured fibroblasts of 13 patients with the Menkes syndrome and two with a new subtype (type IX) of the Ehlers-Danlos syndrome (E-D IX patients) showed many very similar abnormalities in their copper and collagen metabolism. Both cell types had markedly increased copper concentrations and 64Cu incorporation, and this cation accumulated in metallothionein or a metallothionein-like protein, as previously established for Menkes cells. Histochemical staining indicated that copper was distributed diffusely throughout the cytoplasm in both cell types, this location being consistent with the accumulation in metallothionein. Both fibroblast types also had markedly low lysyl oxidase activity and distinctly increased extractability of newly synthesized collagen, whereas no abnormalities were present in cell viability, duplication rate, prolyl 4-hydroxylase activity, or collagen synthesis rate. A high negative correlation (P less than 0.001) was found in the pooled group of Menkes and E-D IX cells between cellular copper concentration (r = 0.804) or 64Cu incorporation (r = 0.863) and the logarithm of lysyl oxidase activity. There was also a high positive correlation (P less than 0.001) between cellular copper concentration and incorporation (r = 0.869). One of the two E-D IX patients was also shown to have similar changes in lysyl oxidase activity and collagen extractability in the skin biopsy specimen, suggesting that the abnormalities observed in cultured cells are similar to those present in vivo. The only distinct abnormality found in the cells of the parents of the E-D IX patients was an increased 64Cu incorporation in those of the mother, this finding being consistent with X-linked inheritance of the disorder.     

A compound-heterozygous Marfan patient: two defective fibrillin alleles result in a lethal phenotype.

We describe here the identification of defined mutations in both alleles of the fibrillin gene (FBN1) in a compound-heterozygote Marfan syndrome (MFS) child who had a very severe form of MFS resulting in death from cardiac failure at the age of 4 mo. The nonconsanguineous parents were both affected with MFS. The father's heterozygous point mutation has earlier been reported to result in W217G substitution, the mother was here shown to carry a heterozygous point mutation resulting in G2627R substitution, and the child had inherited both these mutations. The mutant FBN1 alleles were demonstrated to be transcribed with equal efficiency compared with the normal alleles, but metabolic labeling of fibroblast cultures from the child and both parents showed reduced biosynthesis and secretion of profibrillin. Also, the respective amounts of fibrillin in cell-culture media and extracellular-matrix extracts were markedly diminished, particularly in the cell cultures from father and child. In addition, immunofluorescence analysis of the cell cultures of all three family members revealed a drastically reduced amount of microfibrils, and virtually no visible fibrils could be seen in the case of the compound-heterozygote child. These findings demonstrate incomplete dominance of fibrillin mutations and underline the fatal consequences of the complete absence of normal fibrillin molecules in the microfibrils.