Mutations in DNAH5 account for only 15% of a non-preselected cohort of patients with primary ciliary dyskinesia.

BACKGROUND: Primary ciliary dyskinesia (PCD) is characterised by recurrent infections of the upper respiratory airways (nose, bronchi, and frontal sinuses) and randomisation of left-right body asymmetry. To date, PCD is mainly described with autosomal recessive inheritance and mutations have been found in five genes: the dynein arm protein subunits DNAI1, DNAH5 and DNAH11, the kinase TXNDC3, and the X-linked retinitis pigmentosa GTPase regulator RPGR. METHODS: We screened 89 unrelated individuals with PCD for mutations in the coding and splice site regions of the gene DNAH5 by denaturing high performance liquid chromatography (DHPLC) and sequencing. Patients were mainly of European origin and were recruited without any phenotypic preselection. RESULTS: We identified 18 novel (nonsense, splicing, small deletion and missense) and six previously described mutations. Interestingly, these DNAH5 mutations were mainly associated with outer + inner dyneins arm ultrastructural defects (50%). CONCLUSION: Overall, mutations on both alleles of DNAH5 were identified in 15% of our clinically heterogeneous cohort of patients. Although genetic alterations remain to be identified in most patients, DNAH5 is to date the main PCD gene.

Axonemal beta heavy chain dynein DNAH9: cDNA sequence, genomic structure, and investigation of its role in primary ciliary dyskinesia.

Dyneins are multisubunit protein complexes that couple ATPase activity with conformational changes. They are involved in the cytoplasmatic movement of organelles (cytoplasmic dyneins) and the bending of cilia and flagella (axonemal dyneins). Here we present the first complete cDNA and genomic sequences of a human axonemal dynein beta heavy chain gene, DNAH9, which maps to 17p12. The 14-kb-long cDNA is divided into 69 exons spread over 390 kb. The cDNA sequence of DNAH9 was determined using a combination of methods including 5' rapid amplification of cDNA ends, RT-PCR, and cDNA library screening. RT-PCR using nasal epithelium and testis RNA revealed several alternatively spliced transcripts. The genomic structure was determined using three overlapping BACs sequenced by the Whitehead Institute/MIT Center for Genome Research. The predicted protein, of 4486 amino acids, is highly homologous to sea urchin axonemal beta heavy chain dyneins (67% identity). It consists of an N-terminal stem and a globular C-terminus containing the four P-loops that constitute the motor domain. Lack of proper ciliary and flagellar movement characterizes primary ciliary dyskinesia (PCD), a genetically heterogeneous autosomal recessive disorder with respiratory tract infections, bronchiectasis, male subfertility, and, in 50% of cases, situs inversus (Kartagener syndrome, KS). Dyneins are excellent candidate genes for PCD and KS because in over 50% of cases the ultrastructural defects of cilia are related to the dynein complex. Genotype analysis was performed in 31 PCD families with two or more affected siblings using a highly informative dinucleotide polymorphism located in intron 26 of DNAH9. Two families with concordant inheritance of DNAH9 alleles in affected individuals were observed. A mutation search was performed in these two "candidate families," but only polymorphic variants were found. In the absence of pathogenic mutations, the DNAH9 gene has been excluded as being responsible for autosomal recessive PCD in these families.

No deleterious mutations in the FOXJ1 (alias HFH-4) gene in patients with primary ciliary dyskinesia (PCD).

The transcription factor FOXJ1 (alias HFH-4 or FKHL13) of the winged-helix/forkhead family is expressed in cells with cilia or flagella, and seems to be involved in the regulation of axonemal structural proteins. The knockout mouse Foxj1(-/-) shows abnormalities of organ situs, consistent with random determination of left-right asymmetry, and a complete absence of cilia. The human FOXJ1 gene which maps to chromosome 17q, is thus an excellent candidate gene for Kartagener Syndrome (KS), a subphenotype of Primary Ciliary Dyskinesia (PCD), characterized by bronchiectasis, chronic sinusitis and situs inversus. We have collected samples from 61 PCD families, in 31 of which there are at least two affected individuals. Two families with complete aciliogenesis, and six families, in which the affected members have microsatellite alleles concordant for a locus on distal chromosome 17q, were screened for mutations in the two exons and intron-exon junctions of the FOXJ1 gene. No sequence abnormalities were observed in the DNAs of the affected individuals of the selected families. These results demonstrate that the FOXJ1 gene is not responsible for the PCD/KS phenotype in the families examined.

Primary ciliary dyskinesia: a genome-wide linkage analysis reveals extensive locus heterogeneity.

Primary ciliary dyskinesia (PCD), or immotile cilia syndrome (ICS), is an autosomal recessive disorder affecting ciliary movement with an incidence of 1 in 20000-30000. Dysmotility to complete immotility of cilia results in a multisystem disease of variable severity with recurrent respiratory tract infections leading to bronchiectasis and male subfertility. Ultrastructural defects are present in ciliated mucosa and spermatozoa. Situs inversus (SI) is found in about half of the patients (Kartagener syndrome). We have collected samples from 61 European and North American families with PCD. A genome-wide linkage search was performed in 31 multiplex families (169 individuals including 70 affecteds) using 188 evenly spaced (19cM average interval) polymorphic markers. Both parametric (recessive model) and non-parametric (identity by descent allele sharing) linkage analyses were used. No major locus for the majority of the families was identified, although the sample was powerful enough to detect linkage if 40% of the families were linked to one locus. These results strongly suggest extensive locus heterogeneity. Potential genomic regions harbouring PCD loci were localised on chromosomes 3p, 4q, 5p, 7p, 8q, 10p, 11q, 13q, 15q, 16p, 17q and 19q. Linkage analysis using PCD families with a dynein arm deficiency provided 'suggestive' evidence for linkage to chromosomal regions 8q, 16pter, while analyses using only PCD families with situs inversus resulted in 'suggestive' scores for chromosomes 8q, and 19q.

Trisomy 12 mosaicism confirmed in multiple organs from a liveborn child.

This patient, in whom trisomy 12 mosaicism was confirmed in multiple organs, is the fifth case diagnosed postnatally and the first reported for whom a meiotic origin of the trisomy, maternal meiosis I, was determined. Mosaic aneuploidy was suspected because of pigmentary dysplasia, a frequent but non-specific finding in chromosomal mosaicism. The severe phenotype of this child, who died in infancy with a complex heart malformation, was probably a result of the high percentage of trisomic cells. Cytogenetic and interphase fluorescent in situ hybridization analyses showed a highly variable distribution of aneuploid cells in the nine tissues studied, from none in blood and ovary to 100% in spleen and liver. The trisomy arose meiotically with apparent post-zygotic loss of one of the chromosomes 12; uniparental disomy for this chromosome in the diploid cell line was excluded. The phenotype of the cases reported in living or liveborn individuals has been extremely variable, ranging from the present case, in which the child died in infancy with multiple malformations and pigmentary dysplasia, to a fortuitous finding in an adult studied for infertility. The variation in severity is probably determined by the proportion and distribution of the trisomic cells, which is linked to the timing of the non-disjunctional error.

Chromosome mapping of Rett syndrome: a likely candidate region on the telomere of Xq.

Rett syndrome (RS) is a disease of neurological development. First reported 30 years ago in 1966, its biological and genetic basis remains obscure. RS is commonly thought of as an X linked dominant disorder lethal to hemizygous males. The few familial cases would arise through mosaicism or because of occasional females failing to manifest the disorder through skewed X inactivation in relevant cell types. We have one family where the mother and daughter are affected with RS, and which can be explained according to this hypothesis. If the alternative proposal of Thomas (1996) is correct, that the lack of males affected by such disorders is the result of a high male to female ratio of germline mutations rather than of gestational lethality, then the RS gene should be located on the grandpaternal chromosome. Genomic screening with markers covering the whole X chromosome has been performed. Studies using multiple informative markers indicate that the RS locus is likely to be located close to one of the X chromosome telomeres. Further investigations in eight additional families suggest the most likely region for the RS gene to be is the distal part of Xq (Xq28).

Familial translocation t(Y;15)(q12;p11) and de novo deletion of the Prader-Willi syndrome (PWS) critical region on 15q11-q13.

We describe a 17-year-old girl with mild Prader-Willi syndrome (PWS) due to 15q11-q13 deletion. The deletion occurred on a paternal chromosome 15 already involved in a translocation, t(Y;15)(q12;p11), the latter being present in five other, phenotypically normal individuals in three generations. This appears to be the first case of PWS in which the causative 15q11-q13 deletion occurred on a chromosome involved in a familial translocation, but with breakpoints considerably distal to those of the familial rearrangement. The translocation could predispose to additional rearrangements occurring during meiosis and/or mitosis or, alternatively, the association of two cytogenetic anomalies on the same chromosome could be fortuitous.

Prenatal diagnosis in Switzerland.

Switzerland, with a population of slightly over 7 million, has about 83,000 births per year. There is no comprehensive national registry for prenatal diagnosis (PND) or congenital malformations. Health care is largely organised within each of the 23 countries. Whereas ultrasound screening is available to all pregnant women, the availability of other types of PND is largely determined by proximity to the university medical centres or specialised clinics. Maternal biochemical serum screening is offered by some 15-20 laboratories, and cytogenetic analyses are performed in 8. DNA-based diagnosis is essentially limited to the medical genetics departments/divisions of the 5 university medical schools. It can be estimated that slightly over 10% of gestations are monitored by invasive prenatal diagnostic techniques. The greatest challenge for the future will be the training of the medical and paramedical personnel necessary for the current and future pre- and postnatal diagnostic testing.

The clinical, molecular, and pathological characterisation of a family with two cases of lethal perinatal type 2 Gaucher disease.

It has recently been emphasised that a subset of patients with type 2 Gaucher disease die in the neonatal period. This report describes an Afghani family with two conceptuses having severe, prenatally detected Gaucher disease. Mutational analysis showed that the family carried a known complex allele which included mutations at amino acids L444P, A456P, and V460V. Although glucocerebrosidase RNA was present, an affected fetus had virtually no glucocerebrosidase cross reactive material on western analyses. The severe clinical course and pathology observed in these patients resemble that of the null allele Gaucher mouse, and suggest that the absence of glucocerebrosidase activity results in early death.

Trisomy 3 mosaicism on CVS: case report with literature review and propositions for investigation and counseling.

Chorionic villus sampling performed for advanced maternal age revealed trisomy 3 in 20% of mitoses studied after a semi-direct chromosomal harvest. Amniocytes and cord blood showed a non-mosaic 46,XY karyotype. The birthweight of the normal newborn was at the tenth percentile. Analysis of term placenta by cytogenetics and by fluorescent in situ hybridization (FISH) confirmed the presence of the trisomy 3 in 20% and 12%, respectively, of cells from two peripheral placental biopsies. Placental histology was heterogeneous, some portions showing immature, edematous and undervascularized villi. DNA analysis confirmed the biparental origin of the chromosomes 3 in the child, whose development is normal at 36 months.

Angelman syndrome due to paternal uniparental disomy of chromosome 15: a milder phenotype?

The Angelman syndrome (AS) is a neurological disorder characterized by severe mental retardation, absent speech, seizures, gait disturbances, and a typical age-dependent facial phenotype. Most cases are due to an interstitial deletion on the maternally inherited chromosome 15, in the critical region q11-q13. Rare cases also result from paternal uniparental disomy of chromosome 15. In a group of 14 patients with sporadic AS diagnosed in Switzerland, we found 2 unrelated females with paternal isodisomy for the entire chromosome 15. Their phenotypes were milder than usually seen in this syndrome: one girl did not show the typical AS facial changes; both patients had late-onset mild seizures; as they grew older, they had largely undisturbed gross motor functions, in particular no severe ataxia. Both girls were born to older fathers (45 and 43 years old, respectively). The apparent association of a relatively milder phenotype in AS with paternal uniparental disomy will have to be confirmed by detailed clinical descriptions of further patients.

High incidence of ectopic nucleolar organizer regions in human testicular tumors.

Eight primary testicular germ cell tumors, one teratocarcinoma cell line, and one Leydig cell tumor were studied to determine the importance of modifications of the nucleolar organizer regions (NORs) in human testicular tumors. Cytogenetic analysis after silver staining showed active ectopic NORs in two primary embryonal carcinomas (EC) in the cell line and in single cells of each of two seminomas (S). In one EC, an ectopic NOR was localized to chromosomal region 1q4; the others were on unidentified rearranged chromosomes. All tumors in which ectopic NORs were observed were hyperdiploid and possessed marker chromosomes typical of human germ cell tumors. Quantitative DNA analysis was performed on three tumors: a teratocarcinoma (TC) and the Leydig cell tumor, which had provided no analyzable mitoses, and a seminoma which was cytogenetically diploid. In all three cases, the major populations were hyperdiploid. The results, in combination with those of an earlier study, provide evidence that active ectopic NORs are common in human testicular tumors.

Melanoma associated with ring chromosome 7.

We report the case of a 17-year-old girl with a constitutional chromosome anomaly (ring chromosome 7), associated with multiple pigmented skin lesions, who developed malignant melanoma. Eight other cases of ring chromosome 7 are described in the literature; all present vascular or pigmented skin lesions, but our patient was the first to develop a malignant tumor. Genetic studies in malignant melanoma are discussed, as well as the possible link between a constitutional anomaly of chromosome 7 and the occurrence of malignant melanoma. This association is possibly not fortuitous, particularly since most ring chromosome 7 patients reported to date have pigmented skin lesions.

Cutaneous findings in ring chromosome 7 syndrome.

All 9 cases of ring chromosome 7 syndrome already identified had skin lesions: 7 had vascular lesions, 5 showed large pigmented congenital nevi, 3 had café-au-lait spots and in 1 case there were achromic spots on the trunk. One girl developed malignant melanoma at the age of 17 years. It appears that in patients presenting with growth retardation and pigmented skin lesions, with or without mental retardation, a cytogenetic study is indicated to search for ring chromosome 7, which is probably more frequent than suggested by the literature.