The familial Mediterranean fever protein, pyrin, associates with microtubules and colocalizes with actin filaments.

Familial Mediterranean fever (FMF) is a recessive disorder characterized by episodes of fever and intense inflammation. FMF attacks are unique in their sensitivity to the microtubule inhibitor colchicine, contrasted with their refractoriness to the anti-inflammatory effects of glucocorticoids. The FMF gene, MEFV, was recently identified by positional cloning; it is expressed at high levels in granulocytes and monocytes. The present study investigated the subcellular localization of the normal gene product, pyrin. These experiments did not support previously proposed nuclear or Golgi localizations. Instead fluorescence microscopy demonstrated colocalization of full-length GFP- and epitope-tagged pyrin with microtubules; this was markedly accentuated in paclitaxel-treated cells. Moreover, immunoblot analysis of precipitates of stabilized microtubules with recombinant pyrin demonstrated a direct interaction in vitro. Pyrin expression did not affect the stability of microtubules. Deletion constructs showed that the unique N-terminal domain of pyrin is necessary and sufficient for colocalization, whereas disease-associated mutations in the C-terminal B30.2 (rfp) domain did not disrupt this interaction. By phalloidin staining, a colocalization of pyrin with actin was also observed in perinuclear filaments and in peripheral lamellar ruffles. The proposal is made that pyrin regulates inflammatory responses at the level of leukocyte cytoskeletal organization and that the unique therapeutic effect of colchicine in FMF may be dependent on this interaction. (Blood. 2001;98:851-859)

Polymorphic DNA haplotypes at the human low-density lipoprotein receptor gene locus in Koreans.

Many low-density lipoprotein (LDL) receptor mutations have been identified and characterized, demonstrating a high degree of allelic heterogeneity at this locus. The ability to identify mutant LDL-receptor genes for prenatal diagnosis of familial hypercholesterolemia (FH) or to study the role of the LDL-receptor gene in polygenic hypercholesterolemia requires the use of closely linked restriction fragment lenghth polymorphisms (RFLPs). In the present study nine different RFLPs (TaqI, StuI, HincII, BstEII, AvaII, PvuII, MspIA, MspIB, and NcoI) and a sequence variation at Arg450 were used to clarify the characteristics of the LDL-receptor gene in Koreans. A total of 978 LDL-receptor alleles from 244 members of 43 different pedigrees (15 normal and 28 FH pedigrees) and 245 individuals (187 normal and 58 FH) were analyzed. Frequencies of these polymorphisms did not differ significantly between controls and FH patients. Individually, seven sites--TaqI, BstEII, AvaII, MspIA, MspIB, NcoI and Arg450--had heterozygosity indices ranging from 0.3610 to 0.4601, whereas the PvuII site displayed low levels of polymorphism and StuI was monomorphic. Haplotypes were constructed for 215 individuals of 13 normal and 24 FH pedigrees using the nine polymorphisms. Of 512 (= 2(9)) possible combinations for the nine polymorphic sites, 39 unique haplotypes were detected. The frequency distribution of individual haplotypes ranged from 1/155 (0.65%) to 40/155 (25.8%). The four most common haplotypes accounted for 59.4% of those sampled. Statistical analysis of the haplotypes indicated marked linkage disequilibrium for these 10 sites and throughout the region containing the LDL-receptor gene. Owing to the high degree of linkage disequilibrium over the entire locus, not all RFLPs were informative. We rank each RFLP according to its informativeness and present a strategy for the optimal selection of RFLPs for pedigree analysis.

Identification of mutations including de novo mutations in Korean patients with hypokalaemic periodic paralysis.

BACKGROUND: Hypokalaemic periodic paralysis (hypoPP) is an autosomal dominant disorder involving the abnormal function of ion channels and it is characterized by paralysis attacks of varying severity, accompanied by a fall in blood potassium levels. Linkage analysis showed that the candidate locus responsible for hypoPP was localized to chromosome 1q31-32, and this locus encoded the muscle dihydropyridine-sensitive calcium channel alpha(1)-subunit (CACNA1S). So far, three different mutations in CACNA1S gene have been identified in patients with hypoPP: Arg528His, Arg1239His and Arg1239Gly in Caucasian patients. However, there are few reports about the mutations of CACNA1S gene in other races. METHODS: In this study, four Korean families with five hypoPP patients were screened for mutations of CACNA1S gene with polymerase chain reaction-based restriction analysis and single-strand conformation polymorphism analysis. To determine the mode of inheritance, haplotype analysis was done with three microsatellite markers (D1S1726, CACNL1A3, and D1S1723). RESULTS: Arg528His mutation was detected in three families, and one family had no known mutations. Moreover, for the first time, we detected de novo Arg528His mutations in two out of three families with hypoPP. Haplotype analysis using three microsatellite markers (D1S1726, CACNL1A3, and D1S1723) suggested the occurrence of de novo Arg528His mutations in two of the three families with Arg528His mutation. CONCLUSIONS: Arg528His mutations of CACNA1S, including de novo Arg528His mutations, were found in Korean patients with hypoPP. These results imply that de novo mutation, in addition to non-penetrance, is one of the genetic mechanisms that can explain the previous clinical observation that hypoPP occurs sporadically without family history.

Analysis of mitochondrial DNA deletions in four chambers of failing human heart: hemodynamic stress, age, and disease are important factors.

Mitochondrial DNA (mtDNA) mutations are not only responsible for organ dysfunction due to inefficient energy production but also indicators of metabolic and functional stresses in the organ. To analyze the significance of deletion mutation in human myocardium, we screened the presence of two common deletions (7.4 kb from 8637-16084 nt, 5.0 kb from 8470-13477 nt) in four chambers using long-PCR, and using serial-dilution PCR, measured the amount of deleted mtDNA in normal heart (NL) of brain-dead victims of road accidents (n = 9, age = 10-59) and failing hearts (CHF) of patients who underwent heart transplantation (n = 24, age = 17-63). Frequency of both deletions was higher in ventricles (Vt) than in atria (At) (Vt:At = 25/33:12/33 for 7.4 kb, 19/33:6/33 for 5 kb) (p < 0.05), whereas it was the same in the right and left chambers. In ventricles, both deletions were more frequent among older persons (> 35 yrs) than in younger persons (< or = 35 yrs) (older:younger = 16/20:9/13 for 7.4 kb, 15/20:4/13 for 5 kb) (p < 0.05). In ventricles of failing heart, the 5-kb deletion was more frequent than in those of normal heart (CHF:NL = 17/24:2/9) (p < 0.05), whereas the 7.4-kb deletion was frequent both in failing and normal hearts (CHF:NL = 19/24:6/9). The association of mutation with aging or disease process observed in ventricles was not found in the atria. Although the amount of mutant mtDNA in the left ventricle tended to increase according to a disease process, it was small, at most 1.56% or 0.012% of total mtDNA for a 7.4- or 5-kb deletion, respectively. No deletion was found, however, in lymphocytes from any patient who underwent transplantation. In conclusion, deletion mutation of mtDNA is frequently, but in a small amount, found in the ventricle of older failing heart than in the atrium of younger normal heart. This suggests that hemodynamic stress, age, and disease are factors to induce mtDNA mutation that represents the indicator of stresses on the heart and might turn into a contributor of progressive heart failure under extreme conditions.

Isolation, genomic organization, and expression analysis of the mouse and rat homologs of MEFV, the gene for familial mediterranean fever.

Familial Mediterranean fever (FMF) is a recessive disorder characterized by episodes of fever with serositis or synovitis. Recently the FMF gene (MEFV) was cloned; the protein product, pyrin/marenostrin, is thought to regulate inflammation in myeloid cells. In this manuscript we report the mouse and rat homologs of MEFV. The murine gene contains ten exons with a coding sequence of 2304 bp, while the rat homolog has nine exons with a coding sequence of 2253 bp. A considerable amino acid sequence homology was observed between the mouse and human (47.6% identity and 65.5% similarity) and between the mouse and rat genes (73.5% identity and 82.1% similarity). The predicted rodent proteins have several important domains and signals found in human pyrin, including a B-box zinc finger domain, Robbins-Dingwall nuclear localization signal, and coiled-coil domain. However, perhaps because of an ancient frame-shift mutation, neither the mouse nor the rat protein has an intact C-terminal B30.2 domain, in which most FMF-associated mutations have been found in human MEFV. Nevertheless, like the human gene, mouse Mefv is expressed in peripheral blood granulocytes but not lymphocytes. Consistent with its expression in granulocytes, Mefv was detected at high levels in the primary follicles and marginal zones of the splenic white pulp. Mefv is localized on mouse Chromosome (Chr) 16, region A3-B1, extending a region of synteny with human Chr 16p13.3. Development of knockout and knockin mouse models may provide further insights into the functional evolution of this gene.

Identification of four novel mutations of the low-density lipoprotein receptor gene in Korean patients with familial hypercholesterolemia.

To obtain insight into the genetic variation of the low-density lipoprotein (LDL) receptor gene in Korean patients with familial hypercholesterolemia (FH), we used single-strand conformation polymorphism to screen all 18 exons and a promotor of the LDL receptor gene in 20 unrelated Korean FH patients. Four novel point mutations were detected in 5 FH patients and were characterized by sequence analysis. Of them, one is a nonsense mutation, a Glu-->Stop (CAG-->TAG) at codon 161, and results in a large deletion. The other three, which were a Ala-->Glu (GCG-->GAG) mutation at signal peptide, Cys-->Tyr (TGC-->TAC) at codon 210, and Pro-->Leu (CTG-->CCG) at codon 584, were novel missense mutations, which modified the highly conserved region of the LDL receptor gene. All these mutations were absent in normolipidemic controls and were associated in heterozygote carriers with clinical signs of FH. Identification of these novel mutations provides another example of the molecular heterogeneity of the LDL receptor gene mutations causing FH.

Novel mutations of the PKD1 gene in Korean patients with autosomal dominant polycystic kidney disease.

The gene for the most common form of autosomal dominant polycystic kidney disease (ADPKD), PKD1, has recently been characterized and shown to encode an integral membrane protein, polycystin-1, which is involved in cell-cell and cell-matrix interactions. Until now, approximately 30 mutations of the 3' single copy region of the PKD1 gene have been reported in European and American populations. However, there is no report of mutations in Asian populations. Using the polymerase chain reaction and single-strand conformation polymorphism (SSCP) analysis, 91 Korean patients with ADPKD were screened for mutation in the 3' single copy region of the PKD1 gene. As a result, we have identified and characterized six mutations: three frameshift mutations (11548del8bp, 11674insG and 12722delT), a nonsense mutation (Q4010X), and two missense mutations (R3752W and D3814N). Five mutations except for Q4010X are reported here for the first time. Our findings also indicate that many different mutations are likely to be responsible for ADPKD in the Korean population. The detection of additional disease-causing PKD1 mutations will help in identifying the location of the important functional regions of polycystin-1 and help us to better understand the pathophysiology of ADPKD.

Long-distance PCR-based screening for large rearrangements of the LDL receptor gene in Korean patients with familial hypercholesterolemia.

BACKGROUND: The LDL receptor is a cell-surface protein that regulates plasma cholesterol by specific uptake of LDL particles from the blood circulation. Familial hypercholesterolemia (FH) results from defective catabolism of LDL, which is caused by mutations in the LDL-receptor gene. METHODS: For the rapid and reliable detection of large rearrangements in the LDL-receptor gene, we established a screening method based on long-distance PCR as an alternative to Southern-blot hybridization. Using long-distance PCR, 45 unrelated Korean subjects heterozygous for FH were screened to assess the frequency and nature of major structural rearrangements in the LDL-receptor gene. RESULTS: Two different deletion mutations, FH6 (same type as FH3 and FH311) and FH 32, were detected in four families by long-distance PCR. Detailed restriction mapping and sequence analysis showed that FH6 was a 5.71-kb deletion extending from intron 8 to intron 12 and that FH32 was a 2-kb deletion extending from intron 6 to intron 7. Sequence analysis for the breakpoints of all deletions detected in Korean FH patients showed that only the left arms of the Alu repetitive sequences were involved in the deletion event. CONCLUSIONS: The screening method based on long-distance PCR provides a powerful strategy for the detection of large rearrangements in the LDL-receptor gene and is a rapid and reliable screening alternative to Southern-blot hybridization.

Allelic frequencies of six (CA)n microsatellite markers of the dystrophin gene in the Korean population.

Using the polymerase chain reaction, we examined the allele frequencies and heterozygosities of six (CA)n markers of the dystrophin gene in Koreans. Allele frequencies of these markers were different from those reported for Caucasians. The heterozygosity values for these markers range from 29 to 86%. With the exception of the STR50 marker, these values were lower than those of Caucasians. However, all markers except for the 3'CA marker showed PIC values over 0.5, suggesting a high degree of polymorphism. Therefore, this study will be useful in linkage analysis for Duchenne and Becker muscular dystrophy families in the Korean population.

Three novel small deletion mutations of the LDL receptor gene in Korean patients with familial hypercholesterolemia.

The low-density lipoprotein (LDL) receptor gene from 80 unrelated Korean patients with familial hypercholesterolemia (FH) was analyzed to screen for small structural rearrangements that could not be detected by Southern blot hybridization. Three different small deletions were detected in exon 11 of 3 FH patients and were characterized by DNA sequence analysis. Of them two mutations are in-frame 36-bp (FH 2) and 9-bp (FH 34) deletions that result in the loss of twelve amino acids (from Met510 to Ile521) and three amino acids (Thr513, Asp514 and Trp515), respectively. Both mutations are located in the third of the five YWTD motifs of the LDL receptor gene. The third mutation (FH 400) is a 2-bp deletion that shifts the translational reading frame and results in a prematurely terminated receptor protein. The generation of a 36-bp deletion can be explained by the formation of a hairpin-loop structure mediated by inverted repeat sequences. On the other hand, the mechanism responsible for the 9- and the 2-bp deletions is probably strand-slippage mispairing mediated by short direct repeats. All of these three deletions are novel mutations. Each of the three deletions was detected only in a single pedigree out of 80 FH families analyzed.

Polymorphisms in the human autosomal dominant polycystic kidney disease 2 (PKD2) gene.

Three polymorphisms of the PKD2 (MIM 173910) gene in patients with autosomal dominant polycystic kidney disease are reported: (1) a substitution from ATT (isoleucine) to GTT (valine) at codon 452; (2) a substitution from CGG (arginine) to CAG (glutamine) at codon 848; and (3) a substitution from G to A in intron 4 of the gene. The minor allelic frequencies of codon 452 and intron 4 in the Korean population were estimated to be 0.03 and 0.32, respectively. Although the codon 848 substitution was not observed in 45 unrelated healthy Korean people, the substitution did not cosegregate with the disease phenotype, suggesting that this was a rare, non-deleterious alteration.

Mutation and haplotype studies of familial Mediterranean fever reveal new ancestral relationships and evidence for a high carrier frequency with reduced penetrance in the Ashkenazi Jewish population.

Familial Mediterranean fever (FMF) is a recessive disorder characterized by episodes of fever with serositis or synovitis. The FMF gene (MEFV) was cloned recently, and four missense mutations were identified. Here we present data from non-Ashkenazi Jewish and Arab patients in whom we had not originally found mutations and from a new, more ethnically diverse panel. Among 90 symptomatic mutation-positive individuals, 11 mutations accounted for 79% of carrier chromosomes. Of the two mutations that are novel, one alters the same residue (680) as a previously known mutation, and the other (P369S) is located in exon 3. Consistent with another recent report, the E148Q mutation was observed in patients of several ethnicities and on multiple microsatellite haplotypes, but haplotype data indicate an ancestral relationships between non-Jewish Italian and Ashkenazi Jewish patients with FMF and other affected populations. Among approximately 200 anonymous Ashkenazi Jewish DNA samples, the MEFV carrier frequency was 21%, with E148Q the most common mutation. Several lines of evidence indicate reduced penetrance among Ashkenazi Jews, especially for E148Q, P369S, and K695R. Nevertheless, E148Q helps account for recessive inheritance in an Ashkenazi family previously reported as an unusual case of dominantly inherited FMF. The presence of three frequent MEFV mutations in multiple Mediterranean populations strongly suggests a heterozygote advantage in this geographic region.

The effects of the cholesterol ester transfer protein gene and environmental factors on the plasma high density lipoprotein cholesterol levels in the Korean population.

The cholesteryl ester transfer protein (CETP) is a plasma glycoprotein that transfers neutral lipids between plasma lipoproteins. The distribution of variations in the CETP gene and their influences on lipid levels were investigated among random members of the Korean population (n = 270) whose profiles of environmental factors were known. The frequencies of the major allele at BamHI, EcoNI, TaqIA, TaqIB, New HinfI RFLPs, and the D442G mutation were 0.77, 0.55, 0.84, 0.62, 0.81, and 0.94, in serial order. The significant associations of the BamHI RFLP and the D442G mutation with the plasma high density lipoprotein (HDL) cholesterol levels were observed in this population. Subjects with genotype B2B2 of the BamHI RFLP had significantly lower HDL cholesterol levels than the mean of total subjects. Subjects with D442G mutant allele had a significantly higher HDL cholesterol levels only in males. Analysis of the covariance model (ANOCOVA) showed that allelic variations in the BamHI RFLP and the D442G mutation sites accounted independently for 4.0 and 5.9% of the total inter-individual variation in plasma HDL cholesterol in males (F = 2.29, p = 0.10; F = 3.4, p = 0.03). The effect of the CETP genotype was very high (about 10%), compared to the total effects of sex, body mass index, age, and smoking habit (20%). In conclusion, the genetic variation of the CETP gene is related to the regulation of plasma HDL cholesterol levels and the extent of the effect seems to be different between male and female in the Korean population.

Two partial deletion mutations involving the same Alu sequence within intron 8 of the LDL receptor gene in Korean patients with familial hypercholesterolemia.

Twenty-eight unrelated persons heterozygous for familial hypercholesterolemia (FH) were screened to assess the frequency and nature of major structural rearrangements at the low-density lipoprotein (LDL) receptor gene in Korean FH patients. Genomic DNA was analyzed by Southern blot hybridization with probes encompassing exons 1-18 of the LDL receptor gene. Two different deletion mutations (FH29 and FH110) were detected in three FH patients (10.7%). Each of the mutations was characterized by the use of exon-specific probes and detailed restriction mapping mediated by long-PCR (polymerase chain reaction). Mutation FH29 was a 3.83-kb deletion extending from intron 6 to intron 8 and FH110 was a 5.71-kb deletion extending from intron 8 to intron 12. In FH29, the translational reading frame was preserved and the deducible result was a cysteine-rich A and B repeat truncated protein that might be unable to bind LDL but would continue to bind beta-VLDL. FH110 is presumed to be a null allele, since the deletion shifts the reading frame and results in a truncated protein that terminates in exon 13. Sequence analysis revealed that both deletions have occurred between two Alu-repetitive sequences that are in the same orientation. This suggested that in these patients the deletions were caused by an unequal crossing over event following mispairing of two Alu sequences on different chromatids during meiosis. Moreover, in both deletions, the recombinations were related to an Alu sequence in intron 8 and the deletion breakpoints are found within a specific sequence, 27 bp in length. This supports the hypothesis that this region might have some intrinsic instability, and act as one of the important factors in large recombinational rearrangements.

A new MspIPCR-RFLP in the human LDL receptor gene.

A new two-allele PCR-based MspI restriction fragment length polymorphism (RFLP) was revealed at the human LDL receptor locus. The polymorphic MspI restriction site is located in the 3'-untranslated region of exon 18 and caused by a T to C substitution at nucleotide 3960. This new MspI RFLP may be useful with other informative RFLPs to follow the segregation of the LDL receptor gene in families with hypercholesterolemia.