A new HaeIII polymorphism at the D21S13 locus

Summary DNA markers in the pericentromeric region of human chromosome 21 have shown linkage to a gene for Familial Alzheimer disease (FAD; St. George Hyslop et al. 1987). The limited informativeness of probes for the loci D21S13 and D21S16 have hindered precise mapping of the FAD locus and analysis of non-allelic heterogeneity in FAD (Schellenberg et al. 1988; St. George-Hyslop et al. 1987). We recently described a new EcoRII polymorphism at the D21S13 locus that was very informative in a large FAD pedigree (Pulst et al. 1990a, b). We now report another polymorphism for the D21S13 locus that further increases the informativeness of this locus.     

Linkage studies in familial Alzheimer disease: Evidence for chromosome 19 linkage

A genetic component in the etiology of Alzheimer disease (AD) has been supported by indirect evidence for several years, with autosomal dominant inheritance with age-dependent penetrance being suggested to explain the familial aggregation of affecteds. St. George Hyslop et al. reported linkage of familial AD (FAD) in four early-onset families (mean age at onset [M] less than 50 years). Subsequent studies have been inconsistent in their results; Goate et al. also reported positive lod scores. However, both Pericak-Vance et al.'s study of a series of mainly late-onset FAD families (M greater than 60 years) and Schellenberg et al.'s study failed to confirm linkage to chromosome 21 (CH21). These various studies suggest the possibility of genetic heterogeneity, with some families linked to CH21 and others unlocalized. Recently, St. George Hyslop et al. extended their analysis to include additional families. The extended analyses supported their earlier finding of linkage to CH21, while showing strong evidence of heterogeneity between early-onset (M less than 65 years) and late-onset (M greater than 60 years) FAD families. Because our families did not show linkage to CH21, we undertook a genomic search for an additional locus for FAD. Because of both the confounding factor of late age at onset of FAD and the lack of clear evidence of Mendelian transmission in some of our families, we employed the affected-pedigree-member (APM) method of linkage analysis as an initial screen for possible linkage. Using this method, we identified two regions suggesting linkage: the proximal long arm of chromosome 19 (CH19) and the CH21 region of FAD linkage reported by St. George Hyslop et al. Application of standard likelihood (LOD score) analysis to these data support the possibility of an FAD gene locate on CH19, particularly in the late-onset FAD families. These data further suggest genetic heterogeneity and delineate this region of CH19 as an area needing additional investigation in FAD.     

Exclusion of linkage to the pericentromeric region of chromosome 21 in the Canadian pedigree with familial Alzheimer disease

Summary Alzheimer disease (AD) is a devastating neurodegenerative disease leading to global dementia. The familial form (FAD) has been linked to markers on chromosome 21 in some families, most tightly to the loci D21S16 and D21S13 located close to the centromere of the long arm. In other families the FAD mutation has been excluded from the more telomeric D21S1/S11 region, but not from the centromeric region of chromosome 21. We identified two new restriction fragment length polymorphisms (RFLPs) for the locus D21S13 and have used these RFLPs for the analysis of one of the largest known early-onset FAD pedigrees. We calculated pairwise and multipoint lod scores for the loci D21S13, D21S110, and D21S11. Linkage to this region of chromosome 21 was excluded with maximum negative lod scores of -6.4 at D21S13 and D21S110. Thus, it is unlikely that the FAD mutation in this family is located in the region that has shown linkage in other FAD pedigrees. This result provides evidence for genetic heterogeneity of early-onset FAD or a location of FAD centromeric to D21S13.     

Chromosome 14 and late-onset familial Alzheimer disease (FAD)

Familial Alzheimer disease (FAD) is genetically heterogeneous. Two loci responsible for early-onset FAD have been identified: the amyloid precursor protein gene on chromosome 21 and the as-yet-unidentified locus on chromosome 14. The genetics of late-onset FAD is unresolved. Maximum-likelihood, affected-pedigree-member (APM), and sib-pair analyses were used, in 49 families with a mean age at onset ≥60 years, to determine whether the chromosome 14 locus is responsible for late-onset FAD. The markers used were D14S53, D14S43, and D14S52. The LOD score method was used to test for linkage of late-onset FAD to the chromosome 14 markers, under three different models: age-dependent penetrance, an affected-only analysis, and age-dependent penetrance with allowance for possible age-dependent sporadic cases. No evidence for linkage was obtained under any of these conditions for the late-onset kindreds, and strong evidence against linkage (LOD score ≤ –2.0) to this region was obtained. Heterogeneity tests of the LOD score results for the combined group of families (early onset, Volga Germans, and late onset) favored the hypothesis of linkage to chromosome 14 with genetic heterogeneity. The positive results are primarily from early-onset families. APM analysis gave significant evidence for linkage of D14S43 and D14S52 to FAD in early-onset kindreds (P < .02). No evidence for linkage was found for the entire late-onset family group. Significant evidence for linkage to D14S52, however, was found for a subgroup of families of intermediate age at onset (mean age at onset ≥60 years and <70 years). These results indicate that the chromosome 14 locus is not responsible for Alzheimer disease in most late-onset FAD kindreds but could play a role in a subset of these kindreds.     

Linkage analysis of familial Alzheimer disease, using chromosome 21 markers

Chromosome 21 markers were tested for linkage to familial Alzheimer disease (FAD) in 48 kindreds. These families had multiple cases of Alzheimer disease (AD) in 2 or more generations with family age-at-onset means (M) ranging from 41 to 83 years. Included in this group are seven Volga German families which are thought to be genetically homogeneous with respect to FAD. Autopsy documentation of AD was available for 32 families. Linkage to the 21 q11-q21 region was tested using D21S16, D21S13, D21S110, D21S1/S11, and the APP gene as genetic markers. When linkage results for all the families were summed, the LOD scores for these markers were consistently negative and the entire region was formally excluded. Linkage results were also summed for the following family groups; late-onset (M greater than 60), early-onset (M less than or equal to 60), Volga Germans (M = 56), and early-onset non-Volga Germans (M less than or equal to 60). For the first three groups, LOD scores were negative for this region. For the early-onset non-Volga German group (six families), small positive LOD scores of Zmax = 0.78 (recombination fraction theta = .15), Zmax = 0.27 (theta = .15), and Zmax = 0.64 (theta = .0), were observed for D21S13, D21S16, and D21S110, respectively. The remainder of the long arm of chromosome 21 was tested for linkage to FAD using seven markers spanning the q22 region. Results for these markers were also predominantly negative. Thus it is highly unlikely that a chromosome 21 gene is responsible for late-onset FAD and at least some forms of early-onset FAD represented by the Volga German kindreds.     

Linkage of Familial Schizophrenia to Chromosome 13q32

Over the past 4 years, a number of investigators have reported findings suggestive of linkage to schizophrenia, with markers on chromosomes 13q32 and 8p21, with one recent study by Blouin et al. reporting significant linkage to these regions. As part of an ongoing genome scan, we evaluated microsatellite markers spanning chromosomes 8 and 13, for linkage to schizophrenia, in 21 extended Canadian families. Families were analyzed under autosomal dominant and recessive models, with broad and narrow definitions of schizophrenia. All models produced positive LOD scores with markers on 13q, with higher scores under the recessive models. The maximum three-point LOD scores were obtained under the recessive-broad model: 3.92 at recombination fraction (theta).1 with D13S793, under homogeneity, and 4.42 with alpha=.65 and straight theta=0 with D13S793, under heterogeneity. Positive LOD scores were also obtained, under all models, for markers on 8p. Although a maximum two-point LOD score of 3.49 was obtained under the dominant-narrow model with D8S136 at straight theta=0.1, multipoint analysis with closely flanking markers reduced the maximum LOD score in this region to 2. 13. These results provide independent significant evidence of linkage of a schizophrenia-susceptibility locus to markers on 13q32 and support the presence of a second susceptibility locus on 8p21.     

Linkage and association mapping of the LRP5 locus on chromosome 11q13 in type 1 diabetes

Linkage of chromosome 11q13 to type 1 diabetes (T1D) was first reported from genome scans (Davies et al. 1994; Hashimoto et al. 1994) resulting in P <2.2 x 10(-5) (Luo et al. 1996) and designated IDDM4 ( insulin dependent diabetes mellitus 4). Association mapping under the linkage peak using 12 polymorphic microsatellite markers suggested some evidence of association with a two-marker haplotype, D11S1917*03-H0570POLYA*02, which was under-transmitted to affected siblings and over-transmitted to unaffected siblings ( P=1.5 x 10(-6)) (Nakagawa et al. 1998). Others have reported evidence for T1D association of the microsatellite marker D11S987, which is approximately 100 kb proximal to D11S1917 (Eckenrode et al. 2000). We have sequenced a 400-kb interval surrounding these loci and identified four genes, including the low-density lipoprotein receptor related protein (LRP5) gene, which has been considered as a functional candidate gene for T1D (Hey et al. 1998; Twells et al. 2001). Consequently, we have developed a comprehensive SNP map of the LRP5 gene region, and identified 95 SNPs encompassing 269 kb of genomic DNA, characterised the LD in the region and haplotypes (Twells et al. 2003). Here, we present our refined linkage curve of the IDDM4 region, comprising 32 microsatellite markers and 12 SNPs, providing a peak MLS=2.58, P=5 x 10(-4), at LRP5 g.17646G>T. The disease association data, largely focused in the LRP5 region with 1,106 T1D families, provided no further evidence for disease association at LRP5 or at D11S987. A second dataset, comprising 1,569 families from Finland, failed to replicate our previous findings at LRP5. The continued search for the variants of the putative IDDM4 locus will greatly benefit from the future development of a haplotype map of the genome.     

Linkage and mutational analysis of familial Alzheimer disease kindreds for the APP gene region

A large number of familial Alzheimer disease (FAD) kindreds were examined to determine whether mutations in the amyloid precursor protein (APP) gene could be responsible for the disease. Previous studies have identified three mutations at APP codon 717 which are pathogenic for Alzheimer disease (AD). Samples from affected subjects were examined for mutations in exons 16 and 17 of the APP gene. A combination of direct sequencing and single-strand conformational polymorphism analysis was used. Sporadic AD and normal controls were also examined by the same methods. Five sequence variants were identified. One variant at APP codon 693 resulted in a Glu-->Gly change. This is the same codon as the hereditary cerebral hemorrhage with amyloidosis-Dutch type Glu-->Gln mutation. Another single-base change at APP codon 708 did not alter the amino acid encoded at this site. Two point mutations and a 6-bp deletion were identified in the intronic sequences surrounding exon 17. None of the variants could be unambiguously determined to be responsible for FAD. The larger families were also analyzed by testing for linkage of FAD to a highly polymorphic short tandem repeat marker (D21S210) that is tightly linked to APP. Highly negative LOD scores were obtained for the family groups tested, and linkage was formally excluded beyond theta = .10 for the Volga German kindreds, theta = .20 for early-onset non-Volga Germans, and theta = .10 for late-onset families. LOD scores for linkage of FAD to markers centromeric to APP (D21S1/S11, D21S13, and D21S215) were also negative in the three family groups. These studies show that APP mutations account for AD in only a small fraction of FAD kindreds.     

The Friedreich ataxia gene is assigned to chromosome 9q13-q21 by mapping of tightly linked markers and shows linkage disequilibrium with D9S15.

Chamberlain et al. have assigned the gene for Friedreich ataxia (FA), a recessive neurodegenerative disorder, to chromosome 9, and have proposed a regional localization in the proximal short arm (9p22-cen), on the basis of linkage to D9S15 and to interferon-beta (IFNB), the latter being localized in 9p22. We confirmed more recently the close linkage to D9S15 in another set of families but found much looser linkage to IFNB. We also reported another closely linked marker, D9S5. Additional families have now been studied, and our updated lod scores are z = 14.30 at theta = .00 for D9S15-FA linkage and z = 6.30 at theta = .00 for D9S5-FA linkage. Together with the recent data of Chamberlain et al., this shows that D9S15 is very likely within 1 cM of the FA locus. We have found very significant linkage disequilibrium (delta Std = .28, chi 2 = 9.71, P less than .01) between FA and the D9S15 MspI RFLP in French families, which further supports the very close proximity of these two loci. No recombination between D9S5 and D9S15 was found in the FA families or Centre d'Etude du Polymorphisme Humain families (z = 9.30 at theta = .00). Thus D9S5, D9S15, and FA define a cluster of tightly linked loci. We have mapped D9S5 by in situ hybridization to 9q13-q21, and, accordingly, we assign the D9S5, D9S15, and FA cluster to the proximal part of chromosome 9 long arm, close to the heterochromatic region.     

Proposed stratotype for the base of the highest Cambrian stage at the first appearance datum of Cordylodus andresi, Lawson Cove section, Utah, USA

We propose a candidate for the Global Standard Stratotype-section and Point (GSSP) for the base of the highest stage of the Furongian Series of the Cambrian System. The section is at Lawson Cove in the Ibex area of Millard County, Utah, USA. The marker horizon is the first appearance datum (FAD) of the conodont Cordylodus andresi Viira et Sergeyeva in Kaljo et al. [Kaljo, D., Borovko, N., Heinsalu, H., Khazanovich, K., Mens, K., Popov, L., Sergeyeva, S., Sobolevskaya, R., Viira, V., 1986. The Cambrian–Ordovician boundary in the Baltic–Ladoga clint area (North Estonia and Leningrad Region, USSR). Eesti NSV Teaduste Akadeemia Toimetised. Geologia 35, 97–108]. At this section and elsewhere this horizon also is the FAD of the trilobite Eurekia apopsis (Winston et Nicholls, 1967). This conodont characterizes the base of the Cordylodus proavus Zone, which has been recognized in many parts of the world. This trilobite characterizes the base of the Eurekia apopsis Zone, which has been recognized in many parts of North America. The proposed boundary is 46.7 m above the base of the Lava Dam Member of the Notch Peak Formation at the Lawson Cove section. Brachiopods, sequence stratigraphy, and carbon-isotope geochemistry are other tools that characterize this horizon and allow it to be recognized in other areas.     

An efficient strategy for gene mapping using multipoint linkage analysis: exclusion of the multiple endocrine neoplasia 2A (MEN2A) locus from chromosome 13.

Members of four families in which multiple endocrine neoplasia type 2A (MEN-2A) is segregating were typed for seven DNA markers and one red cell enzyme marker on chromosome 13. Close linkage was excluded between the MEN2A locus and each marker locus tested. By means of multipoint analysis and the genetic map of chromosome 13 developed by Leppert et al., MEN2A was excluded from any position between the most proximal marker locus (D13S6) and the most distal marker locus (D13S3) and from within 12 cMorgans outside these two loci, respectively. However, the support of exclusion within an interval was diminished under the assumption of a substantially larger genetic map in females. The strategy of multipoint analysis, which excluded between 1.5 and 2.0 times more chromosome 13 than did two-point analysis, demonstrates the utility of linkage maps in mapping disease genes.     

The murine MHC encodes a mammalian homolog of bacterial ribosomal protein S13

The mouse major histocompatibility complex (MHC) contains many genes in addition to the classical immune response genes. We have screened overlapping cosmid clones covering 170 kb of the H-2K region for genes expressed in embryonal carcinoma (EC) cells. The Ke-3 gene (Abe et al. 1988) found in this region was further studied by Southern, Northern, and sequence analysis. It is an expressed, intron-containing locus encoding a mouse homolog of the bacterial ribosomal protein S13. This is the first nonorganelle S13 homolog identified in metazoans, and its genomic location has been determined precisely.     

Refined mapping of the gene for autosomal dominant retinitis pigmentosa (RP17) on chromosome 17q22

Linkage analysis was performed on a large Dutch family with autosomal dominant retinitis pigmentosa. Linkage was found to the RP17 locus on chromosome 17q22, which was previously described in two South African families by Bardien et al. (1995, 1997). Assuming that the disease phenotypes in these families are caused by the same gene, the RP17 critical region is refined to a 7.7-cM interval between markers D17S1607 and D17S948. Two positional candidate genes, the retina-specific amine oxidase (RAO) gene (AOC2) and the cone transducin γ gene (GNGT2), were excluded. Received: 7 September 1998 / Accepted: 23 November 1998     

Subregional localization of the chromosome 21 loci D21S24 and D21S26 using physical mapping techniques

Summary We were able to refine the chromosomal position of two existing marker loci, using an extended chromosome 21 somatic cell hybrid panel. The locus D21S26 mapped in the region 21q11.2–q21.1, and the locus D21S24 in 21q22.1–q22.2. Physical and genetic analysis indicated that D21S26 is tightly linked to D21S13 and D21S16, two markers previously linked to familial Alzheimer's disease.     

Mapping of chromosomal loci associated with lipopolysaccharide synthesis and serotype specificity in Vibrio cholerae 01 by transposon mutagenesis using Tn5 and Tn2680

Summary Vibrio cholerae strains of the 01 serotype have been classified into three subclasses, Ogawa, Inaba and Hikojima, which are associated with the O-antigen of the lipopolysaccharide (LPS). The DNA encoding the biosynthesis of the O-antigen, the rfb locus, has been cloned and analysed (Manning et al. 1986; Ward et al. 1987). Transposon mutagenesis of the Inaba and Ogawa strains of V. cholerae, using Tn5 or Tn2680 allowed the isolation of a series of independent mutants in each of these serotypes. Some of the insertions were mapped to the rfb region by Southern hybridization using the cloned rfb DNA as a probe, confirming this location to be responsible for both O-antigen production and serotype specificity. The other insertions allowed a second region to be identified which is involved in V. cholerae LPS biosynthesis.     

Two-Locus Admixture Linkage Analysis of Bipolar and Unipolar Affective Disorder Supports the Presence of Susceptibility Loci on Chromosomes 11p15 and 21q22

Following a report of a linkage study that yielded evidence for a susceptibility locus for bipolar affective disorder on the long arm of chromosome 21, we studied 23 multiply affected pedigrees collected from Iceland and the UK, using the markers PFKL, D21S171, and D21S49. Counting only bipolar cases as affected, a two-point LOD of 1.28 was obtained using D21S171 (θ = 0.01, α = 0.35), with three Icelandic families producing LODs of 0.63, 0.62, and 1.74 (all at θ = 0.0). Affected sib pair analysis demonstrated increased allele sharing at D21S171 (P= 0.001) when unipolar cases were also considered affected. The same set of pedigrees had previously been typed for a tyrosine hydroxylase gene (TH) polymorphism at 11p15 and had shown some moderate evidence for linkage. When information from TH and the 21q markers was combined in a two-locus admixture analysis, an overall admixture LOD of 3.87 was obtained using the bipolar affection model. Thus the data are compatible with the hypothesis that a locus at or near TH influences susceptibility in some pedigrees, while a locus near D21S171 is active in others. Similar analyses in other datasets should be carried out to confirm or refute our tentative finding.     

Eight closely linked loci place the Wilson disease locus within 13q14-q21

Wilson disease (WD) is an autosomal recessive disorder resulting in an accumulation of copper in the liver, brain, and other organs. The WD locus (WND) has previously been linked to esterase D (ESD) and localized to 13q14-22. With the large Centre d'Etude Polymorphisme Humain cohort, a refined map of DNA markers from this region was constructed, with the following locus order: D13S1-D13S21-D13S22-D13S10-ESD-RB-WND-D 13S26-D13S12-D13S2. A significant excess of male recombination was observed between D13S21 and D13S22. Intervals distal to D13S22 showed an excess of female recombination. When these markers were tested on 19 WD families from a variety of ethnic backgrounds, the two closest loci were shown to be RB and D13S26. The retinoblastoma gene locus (RB) was shown to be proximal to WND at a distance of 4.4 centimorgans (cM), and D13S26 was placed distal to WND at a distance of 4.0 cM. ESD was assigned proximally at a distance of 9.4 cM. In all families studied WND was linked to one or more of the loci ESD, RB, or D13S26.     

Linkage of genes for PHI,halothane sensitivity,A-O inhibition,H red blood cell antigens and 6-PGD variants in pigs*

Data from one apparent crossover between S and H, two between PHI and HAL on one side and S on the other, and one between PHI on one side and HAL, S and H on the other, indicate a gene order in pigs of Phi-Hal-S-H-Pgd for genes for PHI, halothane sensitivity, inhibition of expression of A and O, H red blood cell antigens and 6-PGD types. Rasmusen et al. (1980) provided data for a gene order in pigs ofPhi-Hal-H-Pgd for genes for phosphohexose isomerase (PHI) isozyme variants, halothane sensitivity (HAL), H red cell antigens and 6-phosphogluconate dehydrogenase (6-PGD) variants, and suggested that there might be a locus for a gene for inhibition of expression of A and O separate from the locus for H. This is contrary to an earlier proposal by Rasmusen (1972) that the H-system genotype directly influences expression of A and O. Imlah (1980) suggested that the recessive gene for halothane sensitivity has a suppressant effect on the expression of A and O. Andresen (1981) proposed that the locus for inhibition of A and O (for which Rasmusen, 1964, proposed the symbol S) was between the loci for HAL and H types. Data presented in Table 1, which includes haplotypes for three recombinant offspring described by Rasmusen et al. (1980) (883-1, 233-3 and 3864-1) as well as one other recombinant (296-2) provide evidence for the gene order for five genes proposed by Andresen. Types for 6-PGD are listed for all pigs, although they do not provide evidence for gene order in these cases. Male 883-1 (Table 1, and Rasmusen et al., 1980, Table 5) provided the original evidence for recombination between S and H. His phenotype, as well as his genotype as revealed by progeny test (Rasmusen et al., 1980, Table 6) indicated that recombination had occurred between the genes for PHI, HAL and S and the gene for H type in his dam, so that the S locus mapped between H and the loci for the other three traits. The phenotype of one of his sons (233-3, Table 1, and Rasmusen et al., 1980, Table 6) indicated that there had been a recombination between genes for PHI and HAL types on one side and S and H types on the other, providing evidence that the S locus was separate from PHI and HAL as well as H. Another pig listed in Table 1,3864-1, was also described by Rasmusen et al. (1980, Table 9) as a recombinant. This pig provides evidence for recombination between PHI on one side and HAL, S and H on the other, establishing a gene order of Phi-Hal-S-H-Pgd. The last pig listed in Table 1,296-2, is a recombinant comparable to 233-3. The H type of his dam provides markers indicating the recombination was between PHI and HAL on one side and S and H on the other, although the unusual expression of HAL phenotype in both parents of 296-2 makes her haplotypes somewhat uncertain. (Recombination may have been between PHI and HAL rather than as indicated in Table 1.) In spite of incomplete penetrance for HAL (Ollivier et al., 1975; Smith & Bampton, 1977) which makes haplotypes for HAL questionable in some cases, the other genetic markers available are useful to show that recombination has taken place. Without considering the results of halothane testing, if the apparent recombinants are accepted as being as indicated, the order of the genes at the other four loci seems established. Alleles for S types appear to be separable by recombination from those for PHI and H, and the S locus appears to be between the loci for PHI and H. For the five loci, data obtained thus far are cohsistent with a gene order of Phi-Hal-S-H-Pgd.     

Ricerche sul meristema apicale della radice II. II contenuto di coenzimi riboflavinici

Abstract

RESEARCHES ON ROOT APEX MERISTEM. II. RIBOFLAVINE COENZYMES. — FMN and FAD contents have been measured (by the method of BURCH et al.) in the roots of etiolated pea seedlings. It has been found that FMN and FAD content is higher, when referred to fresh weight, in the 2 mm. apical segment than in the next 2–4 mm segment.

On a protein basis, FMN is more abundant in the 2–4 mm segment than in the 0–2 mm apical segment.

The opposite is true for FAD (see table). The apical (meristematic) segment is therefore characterized by a higher FAD/FMN ratio (its value is 1) than the next 2–4 mm segment, where the ratio FAD/FMN is 0.29.     

Identification of crossovers in Wilson disease families as reference points for a genetic localization of the gene

Summary Wilson disease (WD) is an autosomal recessive disorder of copper metabolism. A minimum recombinant analysis using D13S22, ESD, RB1, D13S31, D13S55, D13S26, D13S39, and D13S12, all localized at 13q14-q22, has been carried out in 20WD families of Northwest-European origin. No inconsistencies have been observed with respect to locus order or location of the WD locus (WND) compared with previous linkage studies. D13S31 was mapped as the closest marker proximal to WND, whereas D13S55 and D13S26 were mapped as the closest markers distal to WND. We have identified a crossover between WND and D13S31 in one family and a crossover between WND and D13S55 in another. These crossover sites can be used as reference points for new chromosome 13q14-q21 markers, and are therefore important for a more accurate mapping of the WD locus.