[Concepts for the return of secondary genetic findings in medical diagnostics and research]

High-throughput sequencing of whole genomes is technically already at a high level and is being discussed as a cost-effective alternative to other targeted, analytical procedures for clinical diagnosis of heritable disorders. On the other hand, with whole genome and whole exome sequencing, there is a high likelihood of uncovering secondary findings not associated with the primary aim of the investigation. This article tries to outline the current scientific and technical status of whole genome and whole exome sequencing and of the national and international recommendations concerning the handling of secondary genetic findings which are already available, above all in the research-related context and less so in the clinical context.

Health needs assessment for medical genetic services for congenital disorders in middle- and low-income nations

Medical genetic services for the care and prevention of congenital disorders have received little attention in most middle- and low-income countries to date. In 2010, the World Health Organisation prioritized services for the care and prevention of birth defects in these nations, emphasising their importance in assisting such countries to reach their Millennium Development Goals. Health Needs Assessment is an inclusive, rational, epidemiological-assisted approach for providing information to plan, introduce and beneficially change health care services to improve the health of populations. It is intrinsic to much of the development of health care systems in industrialised nations. Its use by middle- and low-income countries to introduce and develop medical genetic services commensurate with their needs and circumstances would be beneficial. An approach to applying Health Needs Assessment in these circumstances is described.

International variation in physicians' attitudes towards prophylactic mastectomy - comparison between France, Germany, the Netherlands and the United Kingdom

PURPOSE

Prophylactic mastectomy (PM) has proven to be the most effective method to reduce the risk of breast cancer in high-risk women. The present study aimed to present and compare the attitudes towards PM among physicians in France, Germany, the Netherlands and the United Kingdom (UK).

PATIENTS AND METHODS

An international sample of 1196 general practitioners (GPs) and 927 breast surgeons (BS) were surveyed using a mailed questionnaire.

RESULTS

Only 30% of the French and 27% of the German GPs were of opinion that PM should be an option for an unaffected female BRCA1/2 mutation carrier, as compared to 85% and 92% of the GPs in the Netherlands and UK, respectively. Similarly, 78% of the French and 66% of the German BS reported a positive attitude towards PM, as compared to 100% and 97% of the BS in the Netherlands and UK, respectively. In the whole sample of GPs, a positive attitude towards PM was associated with country of residence, being female, and having more knowledge of breast/ovarian cancer genetics, while among BS there was a positive association with country of residence and having more knowledge of breast/ovarian cancer genetics as well, and, in addition, with a higher number of newly diagnosed breast cancer patients last year.

CONCLUSION

These results demonstrated the international variations in the attitude towards PM among physicians. This might reflect that different policies are adopted to prevent breast cancer in women at-risk.

Evaluation of Clinical Manifestations in Patients with Severe Lymphedema with and without CCBE1 Mutations

The lymphedema-lymphangiectasia-intellectual disability (Hennekam) syndrome (HS) is characterised by a widespread congenital lymph vessel dysplasia manifesting as congenital lymphedema of the limbs and intestinal lymphangiectasia, accompanied by unusual facial morphology, variable intellectual disabilities and infrequently malformations. The syndrome is heterogeneous as mutations in the gene CCBE1 have been found responsible for the syndrome in only a subset of patients. We investigated whether it would be possible to predict the presence of a CCBE1 mutation based on phenotype by collecting clinical data of patients diagnosed with HS, with or without a CCBE1 mutation. We report here the results of 13 CCBE1 positive patients, 16 CCBE1 negative patients, who were clinically found to have classical HS, and 8 patients in whom the diagnosis was considered possible, but not certain, and in whom no CCBE1 mutation was identified. We found no statistically significant phenotypic differences between the 2 groups with the clinical HS phenotype, although the degree of lymphatic dysplasia tended to be more pronounced in the mutation positive group. We also screened 158 patients with less widespread and less pronounced forms of lymphatic dysplasia for CCBE1 mutations, and no mutation was detected in this group. Our results suggest that (1) CCBE1 mutations are present only in patients with a likely clinical diagnosis of HS, and not in patients with less marked forms of lymphatic dysplasia, and (2) that there are no major phenotypic differences between HS patients with or without CCBE1 mutations.

A simple clinical model to estimate the probability of Marfan syndrome

BACKGROUND

Marfan syndrome is a heritable connective tissue disease. Definitive diagnosis is complex, and requires sequencing of a large gene, FBN1.

AIM

We aimed to develop a simple model to estimate the pre-test probability of Marfan syndrome.

DESIGN

Prospective cross-sectional study.

METHODS

We applied diagnostic standards for definitive diagnosis or exclusion of Marfan syndrome in 329 consecutive persons. In 208 persons with random assignment to our derivation group, we performed multivariate logistic regression to assess 14 clinical variables for inclusion in a prediction model with derivation of score points from the estimated coefficients. We created cut-offs to classify low, moderate and high probability of Marfan syndrome. For validation, we applied the model to the remaining 121 persons.

RESULTS

We identified seven variables for inclusion in the final model, where we assigned four score points to ectopia lentis, two points to a family history of Marfan syndrome, and one point to previous thoracic aortic surgery, to pectus excavatum, to a wrist and thumb sign, to previous pneumothorax, and to skin striae. In the derivation group 12, 42 and 92% of persons with low (≤1 point), moderate (>1-3.5 points) or high pre-test probability (>3.5 points) had Marfan syndrome, compared to 12, 57 and 91%, respectively, in the validation group. Positive likelihood ratios were 13.96 and 8.54 in the high probability group of the derivation and validation group, respectively.

CONCLUSION

A simple prediction model provides evidence for Marfan syndrome. This model can be used to identify patients who require definitive diagnostic work-up.

[Health insurance companies and medical genetics, what do they want to know? Expert opinions concerning medical genetic services]

Based on the compilation of medical opinions delivered by a medical genetic expert between 2002 and 2010, solicited by private health insurance companies in Germany, an analysis of the main issues raised was made to identify the information needs of company employees with respect to human and medical genetics. The findings are discussed and recommendations for improvement and further training are suggested.

Familial breast cancer: is it time to move from a reactive to a proactive role?

In 2004 the NICE guidelines on familial breast cancer advised Health Care Professionals that they should not actively seek to identify women with a family history of breast cancer. We have carried out a review of the evidence base and a large scale questionnaire survey of health professionals in four European countries. There is overwhelming support amongst GPs and surgeons against the premise that that health care professionals should not be proactive in identifying patients at risk of familial breast cancer. This that suggest the time is right to overturn the NICE decision.

Analysis of phenotype and genotype information for the diagnosis of Marfan syndrome

Marfan syndrome is considered a clinical diagnosis. Three diagnostic classifications comprising first, Marfan genotype with a causative FBN1 gene mutation; second, Marfan phenotype with clinical criteria of the original Ghent nosology (Ghent-1); and third, phenotype with clinical criteria of its current revision (Ghent-2) in 300 consecutive persons referred for confirmation or exclusion of Marfan syndrome (150 men, 150 women aged 35 ± 13 years) were used. Sequencing of TGBR1/2 genes was performed in 128 persons without FBN1 mutation. Marfan genotype was present in 140, Ghent-1 phenotype in 139, and Ghent-2 phenotype in 124 of 300 study patients. Marfan syndrome was confirmed in 94 and excluded in 129 persons consistently by all classifications, but classifications were discordant in 77 persons. With combined genotype and phenotype information confirmation of Marfan syndrome was finally achieved in 126 persons by Ghent-1 and in 125 persons by Ghent-2 among 140 persons with Marfan genotype, and exclusion was accomplished in 139 persons by Ghent-1 and in 141 persons by Ghent-2 among 160 persons without Marfan genotype. In total, genotype information changed final diagnoses in 22 persons with Ghent-1, and in 32 persons with Ghent-2. It is concluded that genotype information is essential for diagnosis or exclusion of Marfan syndrome.

Orphanet – das europäische Portal für seltene Krankheiten

Orphanet ist eine relationale Datenbank über seltene Krankheiten und Arzneimittel für seltene Krankheiten (Orphan Drugs). Die internetbasierte Informationsplattform wurde im Jahr 1997 durch das französische Gesundheitsministerium und INSERM (Institut National de la Santé et de la Recherche Médicale) ins Leben gerufen. Seit dem Jahr 2000 wird Orphanet als europäisches Projekt fortgeführt. Das Konzept der Datenbank basiert auf der Idee, allen beteiligten Interessengruppen Informationen über seltene Krankheiten in Form eines Katalogs von Fachdienstleistungen bereitzustellen. Dieses Angebotsverzeichnis umfasst Informationen über Spezialsprechstunden und Kliniken, Diagnostikangebote, Forschungsprojekte, klinische Studien, Netzwerke, Register und Selbsthilfegruppen aus derzeit 38 Ländern. Die erfassten Leistungen sind unmittelbar mit dem Verzeichnis der seltenen Krankheiten assoziiert, darüber hinaus ist eine umfangreiche Enzyklopädie verfügbar. Alle Informationen sind kostenfrei und in 5 Sprachen über die Website http://www.orpha.net abrufbar.

Prevalence of dural ectasia in 63 gene-mutation-positive patients with features of Marfan syndrome type 1 and Loeys-Dietz syndrome and report of 22 novel FBN1 mutations

Marfan syndrome is an autosomal dominant disorder involving different organ systems. Marfan syndrome type 1 (MFS1) is caused by mutations in the FBN1 gene. Heterozygosity for mutations in the TGFBR1 or TGFBR2 genes cause Loeys-Dietz syndrome (LDS) types 2A and 2B that overlap with MFS1 in their clinical features. The phenotype of MFS1 is defined by the Ghent nosology, which classifies the clinical manifestations in major and minor criteria. Dural ectasia is one of the major criteria for Marfan syndrome but it is rarely tested for. We here report 22 novel and 9 recurrent mutations in the FBN1 gene in 36 patients with clinical features of Marfan syndrome. Sixty patients with identified mutations in the FBN1 gene and three patients with mutations in the TGFBR1 or TGFBR2 genes were examined for dural ectasia. Forty-seven of the 60 patients (78%) with MFS1 showed the dural ectasia criterion and 13 (22%) did not. Thirty-three (55%) patients were suspected of having Marfan syndrome and 24 (73%) of them had dural ectasia. Two of the three patients with LDS had dural ectasia.

Dyschromatosis universalis hereditaria: evidence for autosomal recessive inheritance and identification of a new locus on chromosome 12q21-q23

Dyschromatosis universalis hereditaria (DUH) and dyschromatosis symmetrica hereditaria (DSH) are pigmentary dermatoses most commonly seen in Japan. Both disorders usually show autosomal dominant inheritance, although in some cases autosomal recessive inheritance was reported. DSH was mapped to chromosome 1q21.3, and mutations in the gene ADAR (DSRAD) were identified in Japanese, Chinese and Taiwanese families with autosomal dominant DSH. A second locus for dyschromatosis was mapped on chromosome 6q24.2-q25.2 in two Chinese families initially reported to be affected with DSH, but later suggested to have autosomal dominant DUH. The aim of this study was to investigate whether one of these two loci is involved in the development of DUH in a consanguineous Bedouin family from Saudi Arabia with four affected and three unaffected sibs, clearly pointing to autosomal recessive inheritance. After excluding mutations in ADAR and linkage to the candidate regions on chromosomes 1 and 6, we performed an single nucleotide polymorphism-based genome-wide scan for linkage with other loci. Under the assumption of autosomal recessive inheritance, we have identified a new locus for dyschromatosis on chromosome 12q21-q23 in this Arab family with a maximum logarithm of the odds (LOD) score of 3.4, spanning a distance of 18.9 cM. Our study revealed the first locus for autosomal recessive DUH and supports recent evidence that DSH and DUH are genetically distinct disorders.

Networking for rare diseases: a necessity for Europe

Most rare diseases are life-threatening and chronically debilitating conditions, and the vast majority of them are genetically determined. Their individually low prevalence requires special combined efforts to address them so as to improve diagnosis, care and prevention. Though it is difficult to develop a public health policy specific to each rare disease, it is possible to have a global rather than a piecemeal approach in the areas of scientific and biomedical research, drug research and development, industry policy, information and training, social benefits, hospitalisation and outpatient care. In the recent past, several initiatives at EU and Member States levels have been taken and proved efficient in developing suitable solutions which are now having a positive impact on the quality of life of patients. These initiatives are presented here. They include the establishment of Orphanet, a database of rare diseases and orphan drugs providing an encyclopedia of rare diseases and a directory of associated expert services, the funding of research networks to boost the collaboration between research teams, as well as the funding of networks of clinical centres of reference to better serve the patients and contribute to developing clinical research.

The role of Frank elasticity in cholesteric elastomers

The effect of Frank elasticity on deformations of cholesteric elastomers by mechanical stress applied perpendicular to the helix axis is studied by numerical minimization of the free energy. Above a critical strain, a solution with an only oscillating director is found to be stable in comparison to a distorted helix. At the critical strain, the contractions perpendicular to stress change discontinuously. The critical strain is found to increase with increasing Frank elasticity contribution to the free energy density, and to diverge when the conformation anisotropy of the polymer backbone vanishes. The results are compared with recent experiments which indicated that, in case of weak conformation anisotropies, the Frank elasticity contribution to the free energy cannot be neglected.

Consequences of group fission for the patterns of relatedness among rhesus macaques

When mammalian social groups exceed their optimal size, they often tend to split. In view of the potential evolutionary benefits, it should be more advantageous for animals to stay with kin, rather than nonkin, during such fission events. In the present study, the spontaneous fission of two social groups, R and S, of rhesus macaques living on Cayo Santiago, Puerto Rico, provided the opportunity to compare the kinship structure of the corresponding parent and daughter groups, using information on both maternal and paternal relatedness. In both instances, maternal half-siblings and pairs of animals from the same family were significantly more prevalent in the fission products than in the parent group. During the split of group R, significantly more paternal half-siblings stayed in the remnants of the parent group than joined the seceding group. Our findings are compatible with previous behavioural studies demonstrating that female primates bias their social behaviour more to maternal than to paternal kin, but that both types of half-siblings prefer each other more than unrelated animals. It remains to be clarified by future research, however, whether the observed co-segregation of paternal half-sibs in our study reflects active choice or is a by-product of the group-specific kin structures, prior to fission.

[Genetic diagnosis in medicine. An overview of basic concepts and applications]

Currently, more than half of all known monogenic diseases are characterized at the molecular (DNA) level. This opens the possibility to verify clinically suspected disease at the molecular level, to predict future (late-onset) disorders, to diagnose many diseases prenatally, and to screen the population for genetic traits. Genetic tests that can be performed in Germany, Austria and Switzerland are listed in a database maintained by the German Board of Human Genetics. As of May 2006, 678 different diseases were amenable to DNA-based testing, and 147 institutions offered such tests. The actual genetic test utilisation cannot be determined accurately, but can be deduced from the database of the "Zentralinstitut der Kassenärztlichen Bundesvereinigung". Data have been calculated for the years 1996- 2002. In this time interval, the number of individuals undergoing genetic testing doubled approximately every three years. The total number in 2002 can be estimated at 220,000.

The application of region-specific probes for the resolution of duplication 8p: a case report and a review of the literature

The structural rearrangement in the short arm of a chromosome 8 in a clinically affected patient has been reinvestigated by FISH using whole chromosome painting and region specific YAC probes. An inverted duplication of the segment p22-->p11.2 and a deletion of the subtelomeric region were demonstrated. By this approach, a more detailed resolution of the duplication/deletion 8p was possible. With the application of molecular cytogenetic methods the existence of different duplication segments within the clinical entity of duplication/deficiency 8p can be shown.

Photonic defect modes in cholesteric liquid crystal films

We discuss the properties of photonic defect modes in cholesteric liquid crystals. Twist defects, isotropic defect layers, and combinations of both are considered. After deriving the reflection and transmission properties of the defects, we study the effect of a finite sample thickness on the defect mode's amplitude and on the required polarization of incident light to excite the defect mode.

Generation and characterization of a transgenic mouse with a functional human TSPY

To generate an animal model that is suitable for the analysis of regulation and expression of human testis-specific protein, Y-encoded TSPY, a transgenic mouse line, TgTSPY9, harboring a complete structural human TSPY gene was generated. Fluorescence in situ hybridization and Southern analyses show that approximately 50 copies of the human TSPY transgene are integrated at a single chromosomal site that maps to the distal long arm of the Y chromosome. The transgene is correctly transcribed and spliced according to the human pattern and is mainly expressed in testicular tissue, with spermatogonia and early primary spermatocytes (leptotene and zygotene) as expressing germ cells. TSPY transgenic mice are phenotypically normal, and spermatogenesis is neither impaired nor enhanced by the human transgene. The present study shows that a human TSPY gene integrated into the mouse genome follows the human expression pattern although murine tspy had lost its function in rodent evolution millions of years ago.

Chromosome 18 replaced by two ring chromosomes of chromosome 18 origin

We here describe the first example of the replacement of an autosome by two ring chromosomes originating from the missing chromosome, presented in a patient with a single chromosome 18 and two additional ring chromosomes. Detailed fluorescence in situ hybridization (FISH) analysis revealed the chromosome 18 origin of both ring chromosomes and characterized the small and the large ring chromosome as derivatives of the short and long arm of chromosome 18, respectively. The loss of subtelomeric regions of the short and the long arm of chromosome 18 in the ring chromosomes was confirmed by FISH studies. Molecular studies showed the exclusive presence of the paternal alleles for microsatellite markers located distal to the short and long arm loci D18S843 and D18S474, respectively. This indicates the maternal origin of both rings and provides evidence for substantial deletions of the distal parts of both arms of chromosome 18 in the ring chromosomes. The dysmorphic features of the patient can be explained by these deletions in both chromosome arms, as the clinical findings partly overlap with observations in 18p- and 18q-syndrome and are similar to some cases of ring chromosome 18. Centromere misdivision is suggested as one mechanism involved in the formation of the ring chromosomes.

Search for deletion 22q11.2 in interphase nuclei of buccal mucosa of patients ascertained by isolated cleft palate: a new diagnostic approach

A new approach for the detection of chromosome deletion 22q11.2 in interphase nuclei from buccal mucosa cells obtained by a non-invasive procedure is described. FISH analysis has been performed on samples from a group of 101 patients that presented consecutively for speech therapy and/or surgical correction of cleft palate. A normal result has been obtained in 98 patients; a deletion 22q11.2 was present in three patients (2.8%) with cleft palate.

Estimating the efficacy and efficiency of cascade genetic screening

Screening for genetic variants that predispose individuals or their offspring to disease may be performed at the general population level or may instead be targeted at the relatives of previously identified carriers. The latter strategy has come to be known as "cascade genetic screening." Since the carrier risk of close relatives of known carriers is generally higher than the population risk, cascade screening is more efficient than population screening, in the sense that fewer individuals have to be genotyped per detected carrier. The efficacy of cascade screening, as measured by the overall proportion of carriers detected in a given population, is, however, lower than that of population-wide screening, and the respective inclusion rates vary according to the population frequency and mode of inheritance of the predisposing variants. For dominant mutations, we have developed equations that allow the inclusion rates of cascade screening to be calculated in an iterative fashion, depending upon screening depth and penetrance. For recessive mutations, we derived only equations for the screening of siblings and the children of patients. Owing to their mathematical complexity, it was necessary to study more extended screening strategies by simulation. Cascade screening turned out to result in low inclusion rates (<1%) when aimed at the identification of heterozygous carriers of rare recessive variants. Considerably higher rates are achievable, however, when screening is performed to detect covert homozygotes for frequent recessive mutations with reduced penetrance. This situation is exemplified by hereditary hemochromatosis, for which up to 40% of at-risk individuals may be identifiable through screening of first- to third-degree relatives of overt carriers (i.e., patients); the efficiency of this screening strategy was found to be approximately 50 times higher than that of population-wide screening. For dominant mutations, inclusion rates of cascade screening were estimated to be higher than for recessive variants. Thus, some 80% of all carriers of the factor V Leiden mutation would be detected if screening were to be targeted specifically at first- to third-degree relatives of patients with venous thrombosis. The relative cost efficiency of cascade as compared with population-wide screening (i.e., the overall savings in the extra managerial cost of the condition) is also likely to be higher for dominant than for recessive mutations. This notwithstanding, once screening has become cost-effective at the population level, it can be expected that cascade screening would only transiently represent an economically viable option.

Detection of mutations in the COL4A5 gene by SSCP in X-linked Alport syndrome

Alport syndrome is a progressive renal disease leading to chronic renal failure, which often is accompanied by sensorineural deafness and ophthalmological signs in the form of anterior lenticonus. The X-linked form of the disease is caused by mutations in the COL4A5 gene encoding the alpha5-chain of type IV-collagen. We performed mutation analysis of the COL4A5 gene by PCR-SSCP analysis of each of the 51 exons with flanking intronic sequences in 81 patients suspected of X-linked Alport syndrome including 29 clear X-linked cases, 37 cases from families with a pedigree compatible with X-linked inheritance, and 15 isolated cases. We found a mutation detection rate of 52% (42/81) (58% in males and 21% in females), and 69% (20/29) in families who clearly demonstrated X-linked inheritance. Thirty-six different mutations were found in 42 patients comprising 16 missense mutations, seven frameshifts, three in-frame deletions, four nonsense mutations, and six splice site mutations. Twenty-two of the mutations have not previously been reported. Furthermore, we found one non-pathogenic amino acid substitution, one rare variant in a non-coding region, and one polymorphism with a heterozygosity of 28%. Three de novo mutations were found, two of which were paternal and one of maternal origin.

TSPY variants in six loci on the human Y chromosome

We have studied the structure, organization, and evolution of the human TSPY gene family by mapping three sequence variants identified through RT-PCR analysis onto genomic clones derived from two different YAC contigs. TSPY gene family members occur in at least six locations on the human Y chromosome, and each cluster contains a unique combination of variants. Our data further suggest that an 18-bp tandem duplication found in TSPY exon 1 originated from an unequal sister chromatid exchange between two tandemly arranged TSPY clusters.

Molecular evolution of the murine tspy genes

Molecular aspects of murine evolution were studied by sequencing, and subsequently comparing, introns of the Y-chromosomal tspy genes from Apodemus agrarius, A. sylvaticus, A. flavicollis, Mus platythrix (subgenus Pyromys), M. booduga (subgenus Leggada), and from species of the subgenus Mus, including M. cervicolor, M. macedonicus and M. spretus. Estimates of nucleotide substitution rates in these lineages were in perfect agreement with phylogenetic data previously published by She et al. (1990), Catzeflis et al. (1992; 1993), and Lyon et al. (1996). The only exception was provided by a comparatively late divergence of M. spretus and M. macedonicus. Our data also suggest that M. booduga diverged from the subgenus Mus about 3 Myr ago.

Increased reproductive success of MHC class II heterozygous males among free-ranging rhesus macaques

Gene conversion and balancing selection have been invoked to explain the ubiquitous diversity of the antigen-presenting proteins encoded in the vertebrate major histocompatibility complex (MHC). In the present study, direct evidence for over-dominant selection promoting MHC diversity in primates is provided by the observation that, in a large free-ranging population of rhesus macaques, males heterozygous at MHC class II locus Mamu-DQB1 sired significantly more offspring than homozygotes (the male-specific selection coefficient s equals 0.34). This heterozygote advantage appeared to be independent of the actual male Mamu-DQB1 genotype. No similar effect emerged for a captive group of monkeys of similar genetic background but under veterinary care.

Familial thrombocytosis as a recessive, possibly X-linked trait in an Arab family

Familial thrombocytosis (FT) has previously been described as an autosomal-dominant disorder with manifestations similar to those of sporadic essential thrombocythaemia. We studied an Arab family consisting of four brothers, aged 4-8 years, who had either sustained markedly elevated (> 1000 x 109/l) or moderately elevated (> 500 x 109/l) platelet counts, two healthy sisters and their parents who had normal platelet counts. The four brothers with FT had normal plasma thrombopoietin levels and are currently not presenting with any thrombotic or haemorrhagic complications. Mutation analysis at the thrombopoietin gene (THPO) of the affected family members failed to detect the intron 3 G-->C splice mutation that had been described as causing FT. In addition, segregation analysis using a polymorphic CA marker revealed completely discordant THPO alleles among the affected brothers. We postulate the existence of a new locus for FT whereby the disease is transmitted as a recessive, possibly X-linked trait.

Genotypic and phenotypic spectrum in tricho-rhino-phalangeal syndrome types I and III

Tricho-rhino-phalangeal syndrome (TRPS) is characterized by craniofacial and skeletal abnormalities. Three subtypes have been described: TRPS I, caused by mutations in the TRPS1 gene on chromosome 8; TRPS II, a microdeletion syndrome affecting the TRPS1 and EXT1 genes; and TRPS III, a form with severe brachydactyly, due to short metacarpals, and severe short stature, but without exostoses. To investigate whether TRPS III is caused by TRPS1 mutations and to establish a genotype-phenotype correlation in TRPS, we performed extensive mutation analysis and evaluated the height and degree of brachydactyly in patients with TRPS I or TRPS III. We found 35 different mutations in 44 of 51 unrelated patients. The detection rate (86%) indicates that TRPS1 is the major locus for TRPS I and TRPS III. We did not find any mutation in the parents of sporadic patients or in apparently healthy relatives of familial patients, indicating complete penetrance of TRPS1 mutations. Evaluation of skeletal abnormalities of patients with TRPS1 mutations revealed a wide clinical spectrum. The phenotype was variable in unrelated, age- and sex-matched patients with identical mutations, as well as in families. Four of the five missense mutations alter the GATA DNA-binding zinc finger, and six of the seven unrelated patients with these mutations may be classified as having TRPS III. Our data indicate that TRPS III is at the severe end of the TRPS spectrum and that it is most often caused by a specific class of mutations in the TRPS1 gene.

Mutation screening for prenatal and presymptomatic diagnosis: cystic fibrosis and haemochromatosis

Hereditary haemochromatosis (HH) and cystic fibrosis (CF) are the most common autosomal recessively inherited disorders in Caucasian populations. In its typical form, CF manifests during the first years of life, while the mean age of onset of organ damage is 54 years in HH. Both disorders can be diagnosed presymptomatically utilising biochemical and/or genetic testing. Since approximately 90% of mid-European HH patients are homozygous for only one specific mutation (C282Y) in the candidate gene for HH, genetic testing is simple and sensitive in HH. In CF, molecular testing is currently hampered by the large number (more than 800) of mutations in the CF transmembrane conductance regulator gene. Several studies have been initiated to investigate the potential benefits and the best time and mode of presymptomatic testing for HH and CF.

CONCLUSION

Mutation analysis is widely recommended for presymptomatic diagnosis of cystic fibrosis and hereditary haemochromatosis because of the presumed benefit, although several medical, ethical, social and technical questions warrant further investigations. Prenatal mutation testing is commonly performed for cystic fibrosis but not for hereditary haemochromatosis. Informed consent of tested individuals and the availability of genetic counselling is a prerequisite for any mutation screening approach in either disease.

Immortalization of murine male germ cells at a discrete stage of differentiation by a novel directed promoter-based selection strategy

We developed a novel promoter-based selection strategy that could be used to produce cell lines representing sequential stages of spermatogenesis. The method is based on immortalization and subsequent targeted selection by using differentiation-specific promoter regions. As an example for this approach, a new murine germ cell line (GC-4spc) was established using a vector construct that contains the SV40 large T antigen and the neomycin phosphotransferase II gene under the control of the SV40 early promoter and a spermatocyte-specific promoter for human phosphoglycerate kinase 2, respectively. The GC-4spc was characterized as a cell line at the stage between preleptotene and early pachytene spermatocytes. Transcription of three germ cell-specific expressed genes, Pgk2, proacrosin, and the A-myb proto-oncogene, were detected in the GC-4spc cell line using reverse transcription-polymerase chain reaction. Furthermore, TSPY (human testis-specific protein, Y-encoded) and PGK2 (human phosphoglycerate kinase 2) promoter regions showed different transcriptional activities in the GC-4spc cell line compared with the spermatogonia-derived cell line GC-1spg. Thus, our strategy could be used for immortalization of cells at specific stages of differentiation, allowing production of a series of cultured cell lines representing sequential stages of differentiation in given cell lineages.

Structure and function of TSPY, the Y-chromosome gene coding for the "testis-specific protein"

The TSPY genes are arranged in clusters on the Y chromosome of many mammalian species. TSPY is believed to function in early spermatogenesis and is a candidate for GBY, the putative gonadoblastoma-inducing gene on the Y. The TSPY family forms part of a superfamily, TTSN, with autosomal representatives, highly conserved in mammals and beyond.

Organization and expression of rat Tspy

We have isolated both a full-length rat Tspy cDNA from testicular mRNA by rapid amplification of cDNA ends (RACE) and RT-PCR and a full-length rat Tspy gene from genomic DNA by PCR. In contrast to the mouse, where Tspy is present in a single copy and is apparently functionless, and to man and cattle, where TSPY is organized in a moderately repetitive cluster, the rat Tspy locus apparently consists of one complete functional and one truncated, probably nonfunctional, copy, coherently localized on Yp, as revealed by FISH analysis.

Murine and human TSPYL genes: novel members of the TSPY-SET-NAP1L1 family

Using expressed sequence tag (EST) sequence information, novel genes related to the Y chromosome gene family TSPY were isolated and characterized. Because of a significant homology to TSPY, the novel genes were designated TSPY-Like (TSPYL) and were assigned as new members of the TSPY-SET-NAP1L1 family. A human TSPYL gene was localized on chromosome 6 and a murine Tspyl gene was localized on chromosome 10. Expression of TSPYL was observed in all tissues investigated, as well as early onset during development. Both the human and murine Tspyl homologs lack introns over the entire region so far investigated and are thought to have arisen by an ancient retroposition event. Retroposition of Tspyl genes is supported by the isolation of a murine Tspyl pseudogene on chromosome 12 which also lacks intronic sequences, and by its observed proximity to an R element, a family of dispersed repetitive DNA.

Paternity assessment in rhesus macaques (Macaca mulatta): multilocus DNA fingerprinting and PCR marker typing

Establishing kinship relations in primates using modern molecular genetic techniques has enhanced the ability to scrutinize a number of fundamental biological issues. We screened 51 human short tandem repeats (STRs) for cross-species PCR amplification in rhesus macaques (Macaca mulatta) and identified 11 polymorphic loci with heterozygosity rates of at least 0.6. These markers were used for paternity testing in three social groups (M, R, and S) of rhesus macaques from Cayo Santiago, Puerto Rico. Several consecutive birth cohorts were analyzed in which approximately 200 males were tested for paternity against more than 100 mother/ infant pairs. Despite a combined exclusion rate of more than 99.9% in all three groups, some cases could not be solved unequivocally with the STR markers and additional testing of the MHC-associated DQB1 polymorphism. A final decision became possible through multilocus DNA fingerprinting with one or more of the oligonucleotide probes (GATA)4, (CA)8, and (CAC)5. Paternity assessment by multilocus DNA analysis with probe (CAC)5 alone was found to have limitations in rhesus macaques as regards the number of potential sires which might be involved in a given case. Multilocus DNA fingerprinting requires large amounts of DNA, and the ensuing autoradiographic patterns present difficulties in comparisons across gels and even within the same gel across remote lanes. Computer-assisted image analysis was incapable of eliminating this problem. Therefore, a dual approach to DNA typing has been adopted, using STR markers to reduce the number of potential sires to a level where all remaining candidates can be tested by multilocus DNA fingerprinting on a single gel, preferably in lanes adjacent to the mother/infant pair.

Natal dispersal in rhesus macaques is related to serotonin transporter gene promoter variation

A VNTR polymorphism previously characterized in the promoter region of the human serotonin transporter (SLC6A4) gene was also found to segregate two major alleles (l and s) among the free-ranging rhesus macaques of Cayo Santiago, Puerto Rico. When VNTR genotypes were related to age at male natal dispersal on Cayo Santiago, ss homozygotes (43 of 532 males tested) were found to have left their natal groups significantly earlier (age 57.1 +/- 2.6 months) than carriers of the l allele (ll age, 71.5 +/- 2.1 months; ls age, 63.5 +/- 1.5 months; P = 0.0001). Since migration implies reproductive costs and benefits that change with age at dispersal, migration at an intermediate age might have conferred a heterozygote advantage serving to maintain the VNTR polymorphism via overdominant selection.

Characterization of a new aberration of the human Y chromosome by banding methods and DNA restriction endonuclease analysis

Comparative cytogenetic analyses were performed with ten different banding methods on a previously undescribed, inherited structural aberration of a Y chromosome, and the results compared with those of normal Y chromosomes occurring in the same family. The value of the individual staining techniques in investigations of Y chromosomal aberrations is emphasized. The aberrant Y chromosome analyzed can be formally derived from an isodicentric Y chromosome for the short arm with a very terminal long-arm breakpoint, in which the centromere, an entire short arm, and the proximal region on one long arm was lost. This interpretation was confirmed by determining the amount of the two Y-specific DNA sequences (2.1 and 3.4 kb in length) by means of Hae III restriction endonuclease analysis. The karyotype-phenotype correlations in the men with this aberrant Y chromosome, especially the fertility dysfunctions (oligoasthenoteratozoospermia, cryptozoospermia), are discussed. The possibility of the existence of fertility factors involved in the control of spermatogenesis within the quinacrine-bright heterochromatic region of the Y long arm is presented.

Silencing of the Y-chromosomal gene tspy during murine evolution

We have studied the process of tspy gene silencing in murine evolution. We have isolated functional tspy sequences from Apodemus agrarius, A. sylvaticus, A. flavicollis, and Mus platythrix (subgenus Pyromys) and nonfunctional tspy sequences from species of the subgenus Mus. We present two alternative models as to how tspy may have lost its function in the murine lineage.

Renal polyamine excretion, tubular amino acid reabsorption and molecular genetics in cystinuria

Cystinuria is an autosomal recessive disorder of the tubular and intestinal resorption of cystine, ornithine. lysine and arginine leading to nephrolithiasis. Three cystinuria types can be distinguished by the mode of inheritance (true recessive or intermediate) and by the pattern of the intestinal amino acid transport. In the present study phenotypes were assessed by the urinary excretion of amino acids related to creatinine, the percentage tubular amino acid reabsorption and the urinary excretion of polyamines as a possible indicator of the intestinal transport defect. However, our thorough phenotyping did not reveal more than two cystinuria types. Genotypes were examined in linkage analyses and single-strand conformation polymorphism-based mutation identification. The SLC3A1 mutations M467T and T216M were disease causing in our homozygous patients of type I cystinuria. We can show the association of type I cystinuria with SLC3A1 and of non-type I cystinuria with a yet unidentified gene on chromosome 19q13.1. Our phenotype and genotype analyses provide evidence for only two types of cystinuria in the investigated patient cohort.