Isolation of a Miller-Dieker lissencephaly gene containing G protein beta-subunit-like repeats

Lissencephaly (agyria-pachygyria) is a human brain malformation manifested by a smooth cerebral surface and abnormal neuronal migration. Identification of the gene(s) involved in this disorder would facilitate molecular dissection of normal events in brain development. Type 1 lissencephaly occurs either as an isolated abnormality or in association with dysmorphic facial appearance in patients with Miller-Dieker syndrome. About 15% of patients with isolated lissencephaly and more than 90% of patients with Miller-Dieker syndrome have microdeletions in a critical 350-kilobase region in chromosome 17p13.3 (ref. 6). These deletions are hemizygous, so haplo-insufficiency for a gene in this interval is implicated. Here we report the cloning of a gene (LIS-1, lissencephaly-1) in 17p13.3 that is deleted in Miller-Dieker patients. Non-overlapping deletions involving either the 5' or 3' end of the gene were found in two patients, identifying LIS-1 as the disease gene. The deduced amino-acid sequence shows significant homology to beta-subunits of heterotrimeric G proteins, suggesting that it could possibly be involved in a signal transduction pathway crucial for cerebral development.

Carrier detection of Hunter syndrome (MPS II) by biochemical and DNA techniques in families at risk

DNA based and biochemical diagnosis of MPS II was performed on 13 unrelated families using Southern blotting. The 35S-sulphate accumulation in cultured fibroblasts was investigated and the iduronate-2-sulphatase (IDS) activity in the serum determined. Sixteen patients and 36 females at risk were screened for structural aberrations and by RFLP analysis using the intragenic probe pc2S15 and probes VK23B, VK21A, and II-10 for the flanking loci DXS297, DXS296, and DXS466. Structural alterations were found in the DNA of two patients. One of them showed a major deletion including the whole coding sequence of the IDS gene. An aberrant Southern fragment occurred in the HindIII/pc2S15 blot of the other patient suggesting a new HindIII restriction site by point mutation in an IDS gene intron. Twenty-nine females were confirmed as carriers, and for five women the heterozygous state could be excluded. Prenatal diagnosis can be offered to 27 women if requested.

Structural gene aberrations in mucopolysaccharidosis II (Hunter)

A total of 14 unrelated German patients with X-linked iduronate-2-sulfatase (IDS) deficiency (Hunter syndrome, MPS II) showing variable clinical manifestations was screened for structural gene aberrations by Southern analysis. Using the IDS cDNA clone c2S15 as a probe, no Southern fragments could be detected in blots in the severely affected patient G-65 with respect to DNA digested by HindIII, PstI and TaqI, suggesting a total loss of the IDS structural gene. In this patient, the flanking loci DXS 297, DXS 296 and DXS 466 were tested. The locus DXS 466 is involved in the deletion, whereas both of the other loci are present. A normal 9.0-kb fragment disappeared and an aberrant fragment of 3.5 kb occurred in the HindIII blot of patient G-117. A normal Southern pattern was found in PstI and TaqI blots of this patient. This result can be interpreted as the generation of an additional HindIII restriction site by point mutation in an IDS gene intron.

Evidence supporting tight linkage of X-linked Emery-Dreifuss muscular dystrophy to the factor VIII:C gene

In a large German family with Emery-Dreifuss muscular dystrophy (EDMD) linkage analysis was performed using the factor IX gene (F9), the factor VIII:C gene (F8), the anonymous DNA probe DXS52, and DXS15 as markers. Tight linkage was found between the EDMD locus and the F8 probe (Zmax = 1.19; theta max = 0.00), DXS15 (Zmax = 1.75; theta max = 0.00) and DXS52 (Zmax = 2.26; theta max = 0.00). Weak linkage was found to F9 (Zmax = 0.02; theta max = 0.43). The data from the literature and our results suggest that the gene locus of EDMD is close to F8 (confidence interval theta = 0-0.07). The new linkage data are useful for carrier detection and diagnosis of EDMD patients before onset of major clinical signs.

Deletion analysis of DMD/BMD families from the German Democratic Republic and selected regions of Czechoslovakia and Hungary

Over the last two years we have screened 183 DMD/BMD families requesting prenatal diagnosis. Using cDNA probes cf56a,b we have detected exon deletions in 72 of them. In 62 cases the deletion was also detectable with currently available PCR primers. Deletion analysis for exons 8, 17, and 19, using either PCR or Southern blotting techniques, was performed for 65 of the 111 families which showed no deletions with cf56a,b. Eight of them were deleted for one or more of these exons. PCR offers new possibilities for deletion analysis in families without a living patient using either Guthrie papers or histologically conserved material from the dead patient. In 20 of 25 patients, we observed concordance between the clinical picture and the molecular deletion analysis in accordance with the open reading frame hypothesis. Five patients, however, presented with DMD in spite of our analysis showing an in frame deletion. Carrier determination in families in which DMD is caused by a deletion using linkage, dosage, or breakpoint analysis is discussed.

Prenatal diagnosis of haemophilia A by the polymerase chain reaction using the intragenic hind III polymorphism

A method is described which uses the Hind III polymorphism in intron 19 of the factor VIII gene for genomic family analysis and prenatal diagnosis by the polymerase chain reaction. The primers derived from the exon 19 and 20 sequences allow amplification of the whole intron 19 resulting in a 730 bp fragment. Hind III restriction of this fragment provides fragments of 250 bp or 160 bp and 90 bp respectively, specific for the intragenic Hind III polymorphism. The constant 480 bp fragment can be used as an internal control to circumvent misdiagnosis due to incomplete or failure of restriction. Using this method a prenatal diagnosis of haemophilia A in the first trimester of pregnancy is demonstrated.

Characterization of three new deletions at the 5' end of the HPRT structural gene

In a panel of seven unrelated HPRT-deficient patients three partial deletions of the 5' end of the HPRT structural gene were identified by Southern blot analysis. The deletions could be defined as the loss of exons 1-3, exons 2-3 and exon 3 respectively. In two of the deletion mutations aberrant restriction fragments occurred.

Deletion screening and prenatal diagnosis of Duchenne muscular dystrophy using cDNA probes Cf 23a and Cf 56a

We have screened patients of 14 families at risk for Duchenne muscular dystrophy (DMD) from the northern part of the German Democratic Republic using the cDNA clones Cf 23a and CF 56a. Of the 14 unrelated DMD families, 7 (50%) showed different deletions with these cDNA probes. A prenatal diagnosis by chorionic villi sampling was performed in a DMD family with patients showing a deletion of the 5.4 kb Pst I band detected by the cDNA probe Cf 56a. This band corresponds to a 10 kb exon region of the cDNA probe 8 of Koenig et al. The patient's mother was informative only for the flanking marker 99.6. The male fetus showed the same haplotype and the same deletion as the two patients.

RFLP analysis for diagnosis of haemophilia A in the German Democratic Republic

The frequencies of Bcl I, Hind III and Xba I intragenic polymorphic sites in the population of the GDR were found to be 0.68, 0.38 and 0.48, respectively. No differences in composition and frequencies were detectable at DXS 52 locus in comparison with other Caucasian populations. A strong linkage disequilibrium between the intragenic Bcl I and Hind III sites could be confirmed. The observed heterozygosity for the flanking marker DXS 52 in combination with intragenic Bcl I and Xba I polymorphisms was 0.97. Using these three RFLPs, 122 females at risk in 41 independent haemophilia A families were investigated; 86 of them could be identified and 27 excluded as carriers; 9 females could not be classified. So far, four prenatal diagnoses in the first trimester of gestation have been performed by RFLP analysis.

Prenatal diagnosis of phenylketonuria by haplotype analysis

Prenatal diagnosis of classic phenylketonuria (PKU) was performed after chorionic villus sampling by means of linked restriction fragment length polymorphisms (RFLPs) using the cDNA probe ph PAH 247 (Kwok et al. (1985) Biochemistry, 24, 556-561). We report in this paper a PKU family who were only informative for RFLP analysis by a combination of two RFLPs on the basis of haplotype determination of the normal and mutant phenylalanine hydroxylase (PAH) alleles. The DNA analysis detected a PKU fetus homozygous for mutant PAH alleles and the mother opted for termination in the 12th week of gestation.

Partial deletions of factor VIII gene as molecular diagnostic markers in haemophilia A

A panel of 27 families at risk for haemophilia A was studied by RFLP analysis using the anonymous probe St14.1 (DXS52), a cDNA probe spanning the exons 16 to 19, and a genomic fragment of intron 22. In two patients with severe haemophilia A, who did not form inhibitors, abnormal RFLP patterns were found, that can be interpreted as partial deletions in exons 17 to 19, and intron 22, respectively. In a case with moderate haemophilia A a further partial deletion in intron 22 was found. The significance of the deletions detected as markers for pedigree analysis and prevention of haemophilia A is demonstrated.

Haplotype analysis of classical and mild phenotype of phenylketonuria in the German Democratic Republic

The restriction fragment length polymorphism (RFLP)-haplotypes have been analysed in 16 families from the northern part of the GDR at risk for classical and mild phenylketonuria (PKU). Ten different RFLP haplotypes associated with the normal and mutant phenylalanine hydroxylase (PAH) alleles were identified. Of the 32 mutant alleles analysed, 29 (90.6%) were associated with haplotypes 1, 2, 3 and 4; 53.1% of the mutant alleles were linked with haplotype 2. The distribution of RFLP haplotypes in 16 patients of clinical different PKU phenotypes (classical and mild) is reported.

[Initial results of genetic carrier diagnosis in risk pedigrees with hemophilia A and B in East Germany]

In 7 families at risk for hemophilia A 42 individuals were evaluated by the Taq I polymorphism of the extragenic probe St 14.1 and the Bcl I as well the Hind III polymorphism of the intragenic probe F8e16-19. 15 out of 20 females of the core families were identified as carriers, under them all of the obligate heterozygotes. 5 individuals were excluded as carriers. The heterozygosity for each of the RFLPs was found to be between 30% and 79%. Combining the single data in 96% heterozygosity was found under the individuals tested. A linkage disequilibrium was found between the Bcl I and Hind III polymorphismus of the probe F8e16-19. A family at risk for hemophilia B including 5 individuals was studied using the Taq I and Xmn I polymorphisms of the probe P1. In one of two females the carrier state could be excluded in the other one confirmed.

Reliability of the Tønnesen technique for the identification of Hunter carriers

The procedure for the detection of Hunter carriers suggested by Tønnesen et al. (1982) was checked in different mixtures of normal and Hunter cells as well as by examination of five obligate and five potential Hunter carriers. In the presence of fructose 1-phosphate there was a strict correlation between the proportion of mutant cells in the fibroblast culture and sulphate accumulation, both in artificial cell mixtures and in native cell cultures of Hunter carriers. In all obligate heterozygotes studied, sulphate incorporation was increased by a factor of two. The new technique seems to be suitable for carrier diagnosis. Its limitations are discussed.

[Vitamin B 12 dependent methionine biosynthesis in pseudomonas aeruginosa]

Among methionineless mutants of Pseudomonas aeruginosa strain PAO lacking the ability of methylating homocysteine we found two different types: One of them responding to methionine only, the other one to methionine or vitamin B12 alternatively. That means that P. aeruginosa PAO as well as other B12-producing bacteria (with one exception: Aerobacter aerogenes) use only the B12 pathway (metH) for methionine synthesis. The effect of some cys-auxotrophs equally growing on vitamin B12 as described by Calhoun and Feary (1969) was confirmed for P. aeruginosa PAO by our mutants. In a P. aeruginosa strain of other origin, PAE, neither met- nor cys-mutants responding to B12 have been found, although strain PAE as well as strain PAO excessively synthesize B12.