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The Fifth International workshop on chromosome 9 comprised a gathering of 36 scientists from seven countries and included a fairly even distribution of interests along chromosome 9 as well as a strong input from more global activities and from comparative mapping. At least eight groups had participated in the goal set at the previous workshop which was to improve the fine genetic mapping in different regions of chromosome 9 by meiotic breakpoint mapping in allocated regions and this has resulted in some greatly improved order information. Excellent computing facilities were available and all contributed maps were entered not only into SIGMA (and thence submitted to GDB) but also into a dedicated version of ACEDB which can be accessed on the Web in the form of one of 28 slices into which the chromosome has been arbitrarily divided. It was generally agreed that the amount of data is now overwhelming and that the integration and validation of all data is not only unrealistic in a short meeting but probably impossible until the whole chromosome has been sequenced and fully annotated. Sequence-ready contigs presented at the meeting totalled about 3 MB which is about one fiftieth of the estimated length. The single biggest barrier to integration of maps is the problem of non-standard nomenclature of loci. In the past 2 workshops efforts have been made to compare traditional 'consensus' maps made by human insight (still probably best for small specific regions) with those generated with some computer assistance (such as SIGMA) and those generated objectively by defined computer algorithms such as ldb. Since no single form of map or representation is entirely satisfactory for all purposes the maps reproduced in the published version of the report are confined to one of the genetic maps, in which Genethon and older markers have been incorporated, a Sigma map of the genes as symbols together with a listing of known 'disease' genes on chromosome 9, and a revised assessment of the mouse map together with a list of mouse loci predicted to be on human chromosome 9. One of the 28 ACEDB slices is also shown to illustrate strengths and weaknesses of this approach. Workshop files include not only all maps available at the time but also details of loci and details of the meiotic breakpoints in the CEPH families (http:/(/)www.gene.ucl.ac.uk/scw9db.shtml) .

High-resolution maps integrated with the enhanced location data base software ( ldb+ ) give improved estimates of genetic parameters and reveal characteristics of cytogenetic bands. Chiasma interference is intermediate between Kosambi and Carter–Falconer levels, as in Drosophila and the mouse. The autosomal genetic map is 2832 and 4348 centimorgans in males and females, respectively. Telomeric T-bands are strikingly associated with male recombination and gene density. Position and centromeric heterochromatin have large effects, but nontelomeric R-bands are not significantly different from G-bands. Several possible reasons are discussed. These regularities validate the maps, despite their high resolution and inevitable local errors. No other approach has been demonstrated to integrate such a large number of loci, which are increasing at about 45% per year. The maps and the data and software from which they are constructed are available through the Internet ( http://cedar.genetics.soton.ac.uk/public_html ). Successive versions of this location data base may also be accessed on CD-ROM.

Linkage analysis in twenty-five families with acute (type I) spinal muscular atrophy (SMA) showed that the mutant gene responsible for the disorder is tightly linked to the D5S39 locus. The mutation(s) causing the intermediate (type II) and juvenile chronic (type III) forms of SMA were also mapped to DNA marker D5S39 on chromosome 5 (5q12-q14). Thus, the three forms, which have been differentiated clinically on the basis of age of onset and clinical course, are most probably due to different mutations at a single locus on chromosome 5. Prenatal diagnosis of SMA type I will now be possible.

The availability of more and more reliable obstetrical echographies makes now possible to screen fetuses for microphtalmies and anophtalmies. More over, by mean of linkage studies with DNA markers within a family, we can identify the women who will transmit X-linked diseases, and realize a prenatal diagnosis. This technology can be applied to the following ophthalmological diseases: the X-linked retinoschisis, the choroideremia, the ocular albinism, the Noorie disease, and recently the retinoblastoma. From now on, the use of such a technology which makes it possible to detect ophthalmological diseases in the fetuses, is posing ethical problems especially in case of diseases without any survival prognosis involvement.

Autosomal dominant forms of retinitis pigmentosa appear among the most frequent types of retinal degenerations. Two clinical subtypes have been recognized, namely the early onset, severe form (type I) and the late onset, moderate form (type II). A linkage between the D3S47 probe (C17) with the gene of the type I has been recently demonstrated by Humphries et al., 1989. Here, two families with type II of the disease have been tested for possible allelism at the D3S47 locus. A negative lod-score was found with this probe and a linkage with this region could be excluded. These results support the hypothesis of a genetic heterogeneity in autosomal dominant forms of retinitis pigmentosa.

Data from the expression of P1, P and Pk antigens on somatic cells in culture are presented. A tentative biosynthetic pathway of the P system is proposed, where the P antigen is the precursor of Pk specificity. The expression of the Pk antigen, which appears to be a public antigen in skin fibroblasts, is controlled on red blood cells and lymphocytes by a proposed Ff system.

Heritable disorders of collagen include Ehler-Danlos syndromes (11 types are actually known), Larsen syndrome and osteogenesis imperfecta. Their clinical, genetic and biochemical features are reviewed. Marfan syndrome is closely related to heritable disorders of collagen.

To test Knudson's hypothesis that two successive mutations are involved in retinoblastoma, we studied the data on 899 cases. Some of the findings appeared to differ from those that might be expected if Knudson's hypothesis were correct. Certain criticisms of Knudson's methodology and model were suggested. Alternative explanations proposed were 1) the role of the sequence in which mutations occur, and 2) the possibility of three mutational events.

Recurrence risks were estimated for some congenital malformation from a multifactorial model according to the method given by Smith (1971). Risks were estimated for cleft lip with or without cleft palate, cleft palate alone, anencephaly and spina bifida from data on frequency and heritability collected in France. Results are given in tables representing risks for some 180 specific family histories.

To increase the efficiency of the human gene mapping, a panel of 25 man-rodent hybrids was selected out of 200 independent man-rodent hybrids produced in our laboratory since 1969. The hybrid panel was selected in such a fashion as to allow the asignment of a human marker M by respecting the two following complementary criteria: correlation between M and a chromosome and exclusion of the other chromosomes. The panel characteristics allowing the use of these two criteria were presented and discussed. A first series of enzyme markers were analysed to test the validity of the hybrid panel for the human gene mapping. The different possibilities and limits of the hybrid panel were also discussed, especially for the assignment of markers with DNA probes.

A retrospective study of 20,591 live born babies and still birth was made in order to estimate the incidence of congenital malformations total and by type diagnosed at birth. The total incidence is 1,74 p. 100. The sex ratio, the mean birth rank and parental ages were computed for the different types of malformation and in the control group. The birth weight was low in case of severe malformation. It was found that malformations were associated with significantly raised abortions and still birth rates among previous pregnancies.

The frequency of retinoblastoma was estimated in southwest France (Midi-Pyrénées) during the 1950-1969 period. Twenty-three cases were detected among 507 157 liveborns. After correcting for the probability of ascertainment of patient, the estimated frequency is 1 per 15 849 births. The proportion of unilateral cases is estimated 91 percent after correcting for the higher probability of ascertaining bilateral cases.

From a study of 195 unselected cases of idiopathic squint, the authors distinguish three types of squint (simple, accommodative, and with amblyopia). Both sexes are equally affected, the age of onset is later in accommodative squint than in the other two types. The percentage of familial cases (65.4%) is comparable whatever the type of squint involved, the sex of the subjects or the age of onset. The family study and the complex segregation studies show that the hypothesis of dominant autosomal inheritance with incomplete penetrance is the most probable for the three types, but they do not affirm that three distinct entities are involved.

A retrospective study of 324 cases of chorioretinal heredodegeneration of all kinds shows an associated pathology in 44% of cases. These associated anomalies point out the need of a complete physical examination, a familial inquest keeping in mind genetic counseling. They are a good model for a high resolution cytogenetic study to find microdeletions which can allow to precise the genome's map.

An anonymous DNA probe PAS45 was isolated. This probe detects an RFLP with two alleles 1 and 2 at the same locus, with the different restriction enzymes (Bg1II, EcoRI, HindIII, PstI, MspI, XbaI). The observed polymorphism is explained by a chromosome rearrangement involving these enzyme cleavage sites. The frequency of alleles 1 and 2 was 0.875 and 0.125, respectively, in a sample of 48 unrelated individuals in France. Codominant inheritance of alleles 1 and 2 was demonstrated in 13 families with 30 offspring. The PAS45 probe was localized on chromosome 13 by somatic cell hybrid analysis and on 13q31 by in situ hybridization. The rearrangement on 13q31 is present in one out of four healthy individuals in France.

Lysinuric protein intolerance is an autosomal recessive disease, due to a defect in intestinal, renal and hepatic dibasic amino acid transport. Two new cases in the same family are reported. The disease appears progressively during the first months of life with failure to thrive, anorexia, vomiting, diarrhea, hepatosplenomegaly, muscular weakness, osteoporosis, anemia, leukothrombocytopenia, hyperammonemia and orotic aciduria after a high-protein intake. Hyperdibasicamino-aciduria was associated with subnormal plasma concentrations of the same aminoacids. Oral l-arginine, l-ornithine, l-lysine, and lysyl-glycine loads confirmed the diagnosis. The supplementation of the diet with l-citrulline resulted in normal levels of blood ammonia. However, hepatosplenomegaly, muscular weakness, osteoporosis remained unchanged and growth was not improved. These may be due to lysine deficiency.

A familial study was undertaken on 382 probands with transposition of the great vessels, 348 with coarctation of the aorta and 143 with hypoplastic left heart syndrome. It allowed to assess in sibs the frequency of identical congenital heart diseases (respectively 0.15, 0.42 and 3.41%) and of all 7.32%). The epidemiological study did not provide further data worth noting. At the origin of the transposition of the great vessels, tetratogenetic factors are added to genetic factors, whose part is of little importance; hypoplastic left heart syndromes are heterogeneous (recessive autosomal transmission, chromosome abnormalities, sporadic cases). Coarctations of the aorta, which are dependent on different mechanisms are also heterogeneous. It is possible that common factors, whether hereditary or not, play a part on one hand in hypoplastic left heart syndromes and coarctations of the aorta, and, on the other hand, in some congenital heart diseases.

The authors report the cases of two unrelated children 16 and 5 years of age respectively, affected with hypertyrosinaemia type II. This condition is characterized by palmo-plantar hyperkeratosis associated with a herpetiform keratitis. The diagnosis is based on the finding of hypertyrosinaemia and hypertyrosyluria, and may be confirmed by their biopsy findings of a cytoplasmic tyrosine amino-transferase deficiency. It is a hereditary autosomal recessive disease. A low phenylalanine and tyrosine diet produced a spectacular improvement but the ocular complications could have been avoided by an earlier diagnosis.

The clinical features and biological results in a second patient with a metabolic defect of the molybdenum cofactor are described. The first case was reported in 1978 by Duran et al. Their clinical description was similar with early encephalopathy and myoclonial and dislocation of the lens. Biologically, this condition is characterised by secondary hypo-uricemia and hypo-uricuria due to xanthine oxidase deficiency and by sulphituria, resulting from sulphite oxidase deficiency. These two enzymes have a common hepatic molybdenum cofactor, the structure and metabolism of which are only partially known.

The authors report their own experience as regard to the genetic counseling for consanguineous marriages. They observe that outpatients still marry and procreate despite the medical advices.

Multiple carboxylases deficiency, a recently identified metabolic disease in infants, can be cured by the administration of biotine, a cofactor of the carboxylases: pyruvate, propionyl coenzyme A (CoA), methylcrotonyl CoA, and acetyl CoA. The disorder presents as alopecia, associated with chronic candidosis, psychomotor retardation, and frequent episodes of ketoacidosis coma which responded to biotine treatment. Biological signs, related to the deficiency of the individual enzymes, are observed as hyperlactacidemia, propionic aciduria, and methylcrotonylglycinuria. The metabolic basis of this vitamin-dependent size is still obscure, but the research stimulated by this new disease should clarify the still poorly understood physiological role of this vitamin in humans.