Novel and recurrent TRPV4 mutations and their association with distinct phenotypes within the TRPV4 dysplasia family.

BACKGROUND: Mutations in TRPV4, a gene that encodes a Ca(2+) permeable non-selective cation channel, have recently been found in a spectrum of skeletal dysplasias that includes brachyolmia, spondylometaphyseal dysplasia, Kozlowski type (SMDK) and metatropic dysplasia (MD). Only a total of seven missense mutations were detected, however. The full spectrum of TRPV4 mutations and their phenotypes remained unclear. OBJECTIVES AND METHODS: To examine TRPV4 mutation spectrum and phenotype-genotype association, we searched for TRPV4 mutations by PCR-direct sequencing from genomic DNA in 22 MD and 20 SMDK probands. RESULTS: TRPV4 mutations were found in all but one MD subject. In total, 19 different heterozygous mutations were identified in 41 subjects; two were recurrent and 17 were novel. In MD, a recurrent P799L mutation was identified in nine subjects, as well as 10 novel mutations including F471del, the first deletion mutation of TRPV4. In SMDK, a recurrent R594H mutation was identified in 12 subjects and seven novel mutations. An association between the position of mutations and the disease phenotype was also observed. Thus, P799 in exon 15 is a hot codon for MD mutations, as four different amino acid substitutions have been observed at this codon; while R594 in exon 11 is a hotspot for SMDK mutations. CONCLUSION: The TRPV4 mutation spectrum in MD and SMDK, which showed genotype-phenotype correlation and potential functional significance of mutations that are non-randomly distributed over the gene, was presented in this study. The results would help diagnostic laboratories establish efficient screening strategies for genetic diagnosis of the TRPV4 dysplasia family diseases.

Potential role of chemerin in recruitment of plasmacytoid dendritic cells to diseased skin.

Interferon alpha-producing plasmacytoid dendritic cells (pDC) are crucial contributors to pro-inflammatory or tolerogenic immune responses and are important in autoimmune diseases such as psoriasis. pDC accumulate in the lesional skin of psoriasis patients, but are rarely found in the affected skin of patients with atopic dermatitis (AD). While homeostatic chemokine CXCL12 and inducible pro-inflammatory CXCR3 chemokine ligands may regulate pDC influx to psoriatic skin, the mechanism responsible for selective pDC recruitment in psoriasis vs. AD remains unknown. Circulating pDC from normal donors express a limited number of chemoattractant receptors, including CXCR3 and CMKLR1 (chemokine-like receptor 1). In this work, we demonstrate that circulating pDC from normal donors as well as psoriasis and AD patients express similar levels of CXCR3 and responded similarly in functional migration assays to CXCL10. We next found that blood pDC from normal, AD, and psoriasis patients express functional CMKLR1. In contrast to normal skin, however, lesional skin from psoriasis patients contains the active form of the CMKLR1 ligand chemerin. Furthermore, in affected skin from psoriatic patients the level of active chemerin was generally higher than in AD skin. Taken together, these results indicate that local generation of active chemerin may contribute to pDC recruitment to psoriatic skin.

[Skeletal dysplasias. The network SKELNET]. / Skelettdysplasien. Das Netzwerk SKELNET.

The network concept of SKELNET was developed to meet the problems and requirements encountered caring for patients with skeletal dysplasias. Skeletal dysplasias are a clinically and genetically extremely diverse group of chronic genetic diseases, which primarily affect the development of the skeleton. The rarity, extensive heterogeneity and complex pathophysiology have made these conditions a challenge to diagnose and study. They represent a group of 200 to 300 specific disorders with patients located all across Germany. So far the diagnostic process in Germany relies on a few specialists who evaluate the X-rays and clinical picture of the patient. In addition, diagnostic tests are restricted to a few laboratories across Europe. Consequences are low efficiency in diagnosis, clinical management, treatment, follow-up and scientific knowledge resulting in extremely prolonged periods between upcoming symptoms and correct diagnosis, and probably a high number of unknown and insufficiently treated cases. The improvement of cooperation among the experts is one of the key points to optimize diagnostic procedures. As the cooperating clinical and scientific specialists are at various locations in Germany, one of the major efforts is to channel the different levels of clinical and research information, making patient data files accessible and transparent to experts. This approach aims at the development of new strategies for all-embracing high level patient care fulfilling all requirements concerning the protection of personal data.

A familial case of achondrogenesis type II caused by a dominant COL2A1 mutation and "patchy" expression in the mosaic father.

Achondrogenesis type II (ACG2) is the most severe disorder that can be produced by dominant mutations in COL2A1. We report on four pregnancies of an apparently healthy, nonconsanguineous young couple. The father had scoliosis as a child, and has slight body disproportion with short trunk. The first child was born at 32 weeks and died neonatally. In the second pregnancy, short limbs and fetal hygroma were noted on ultrasound at 17 weeks' gestation. Similar findings were observed in the third fetus. Clinical, radiological, and histological evaluation of the fetuses after termination of the pregnancies showed findings consistent with ACG2. Molecular analysis of genomic DNA extracted from amniotic cells of the second and third fetuses revealed heterozygosity for a 10370G > T missense mutation (G346V) in the COL2A1 gene. This mutation was also found in the father, as a mosaic. The couple had a fourth pregnancy, and at 11 weeks fetal hydrops with a septated cystic hygroma were obvious. DNA from CVS demonstrated the same COL2A1 mutation.

Oncogene-blocking therapies: new insights from conditional mouse tumor models.

Identification of oncogene dependent signaling pathways controlling aggressive tumor growth has led to the emergence of a new era of oncogene-blocking therapies, including Herceptin and Gleevec. In the recent years conditional mouse tumor models have been established that allow switching-off the expression of specific oncogenes controlling tumor growth. The results may have two important implications for oncogene-blocking therapies: (i) downregulation of oncogenes, for instance HER2, MYC, RAS, RAF, BCR-ABL or WNT1, usually leads to a rapid tumor remission. However, it was observed that the initial remission was followed by recurrent tumor growth in most studies. Interestingly, different oncogenes controlled tumor growth in the recurrent than in the primary tumors. This could explain the astonishing clinical observation that inhibitors of a broader spectrum of protein kinases (so-called: "dirty inhibitors") may be superior over highly specific substances. Due to their additional "unspecific" inhibition of a broader spectrum of kinases, they may hamper the escape mechanisms by antagonizing also the pathways controlling recurrent tumor growth. (ii) Experiments with cell systems that allow switching-on oncogene expression point to a so far possibly underestimated cancer drug target: the dormant tumor cell. Oncogene expression (for instance: NeuT or RAS) led to a phenomenon named oncogene-induced senescence or dormancy. Dormant cells are unresponsive to mitogenic stimuli. Importantly, such cells are not at all ready to die, but can remain viable for extended periods of time. Recently, dormant tumor cells have been shown to be more resistant to stresses such as hypoxia or exposure to cytostatic drugs. It still is a matter of debate if and under which conditions dormant tumor cells can be "kissed to life". If these cells contribute to carcinogenesis, it will be important to identify substances specifically killing senescent cells. This review will focus on the possible relevance of senescence both as a pre-oncogenic condition and also for therapy.

Du Pan syndrome phenotype caused by heterozygous pathogenic mutations in CDMP1 gene.

Du Pan syndrome is a rare acromesomelic dysplasia with characteristic clinical and radiographic findings. It is inherited as an autosomal recessive trait. Almost all the patients reported have been from Muslim countries. We report on a female and her child with Du Pan syndrome from a Caucasian, Polish family. Three new heterozygous mutations clustered on one allele of the CDMP1 gene were identified in the affected individuals resulting in the first familial case with dominant Du Pan syndrome. A possible synergistic effect of the cis-acting mutations located in the active domain of the mature CDMP1 protein is likely to be responsible for the clinical expression of the disorder.

A disorder resembling pseudoachondroplasia but without COMP mutation.

Pseudoachondroplasia (PA) is an autosomal dominant skeletal dysplasia characterized by disproportionate short stature, generalized ligamentous laxity, irregular epi-metaphyseal ossification, and vertebral anomalies that regress with age. It usually manifests in the second year of life or later. The clinically and radiographically variable disorder is caused by mutations in the COMP gene. Parental gonadal mosaicism may lead to recurrence of the disorder in children of unaffected parents. Here, we describe sibs with bone changes similar to those seen in very severe PA born to clinically and radiographically unaffected parents. Sequencing of all 19 exons of the COMP gene failed to disclose a mutation. The sibs appear to be affected by a disorder resembling PA but resulting from a defect of an extracellular matrix protein other than COMP. It may be suspected in patients with unusually severe dwarfism, severe epi-metaphyseal abnormalities, and persistent platyspondyly.

4-Epidoxycycline: an alternative to doxycycline to control gene expression in conditional mouse models.

Since the pioneering work by Gossen and Bujard in 1992 demonstrating the usefulness of the Escherichia coli derived tet resistance operon for regulating gene expression a large collection of doxycycline-controlled transgenic mice has been established. Gene switching in eukaryotic tissue culture cells or mice requires administration of tetracycline, anhydrotetracycline or doxycycline to efficiently inactivate the transactivator protein tTA (TET-OFF system) or alternatively to activate the reverse transactivator protein rtTA (TET-ON system). However, the antibiotic activity of doxycycline can create an imbalance of the intestinal flora, resulting in diarrhoea and in a smaller number of animals in colitis. Previous studies reported that 4-epidoxycycline (4-ED), a hepatic metabolite of doxycycline, does not function as an antibiotic in mice. This gave us the idea that 4-ED might be useful for controlling gene expression in mice without the unwanted antibiotic side effect. To study the applicability of 4-ED for control of gene expression we used cell lines expressing the oncogene HER2 under control of tTA (TET-OFF) as well as rtTA (TET-ON). 4-ED and doxycycline were similarly efficient in switching on or -off HER2 expression. In vivo we used a conditional mouse model that allows switching off HER2 in tumor tissue. We show that (i) doxycycline, 7.5mg/ml in drinking water (used as a positive control), (ii) 4-ED, 7.5mg/ml in drinking water, (iii) 4-ED, 10mg/kg body weight, s.c., and (iv) anhydrotetracycline, 10mg/kg, s.c. (used as a second positive control), were similarly efficient. Using mice with tumor volumes of 1.6cm(3) all four schedules led to a tumor remission of more than 95% within 7 days. In conclusion, 4-ED is similarly efficient as doxycycline to control gene expression in vitro and in mice. Since 4-ED lacks the antibiotic activity of doxycycline it may help to avoid adverse side effects and selection of resistant bacteria.

RNAi knock-down mice: an emerging technology for post-genomic functional genetics.

RNA interference (RNAi) has been extensively used for sequence-specific silencing of gene function in mammalian cells. The latest major breakthrough in the application of RNAi technology came from experiments demonstrating RNAi-mediated gene repression in mice and rats. After more than two decades of functional mouse research aimed at developing and continuously improving transgenic and knock-out technology, the advent of RNAi knock-down mice represents a valuable new alternative for studying gene function in vivo. In this review we provide some basic insight as to how RNAi can induce gene silencing to then focus on recent findings concerning the applicability of RNAi for regulating gene function in the mouse. Reviewed topics will include delivery methods for RNAi-mediating molecules, a comparison between traditional knock-out and innovative transgenic RNAi technology and the generation of graded RNAi knock-down phenotypes. Apart from the exciting possibilities RNAi provides for studying gene function in mice, we discuss several caveats and limitations to be considered. Finally, we present prospective strategies as to how RNAi technology might be applied for generating conditional and tissue-restricted knock-down mice.

Improved definition of chromosomal breakpoints using high-resolution multicolour banding.

Characterisation of chromosome rearrangements using conventional banding techniques often fails to determine the localisation of breakpoints precisely. In order to improve the definition of chromosomal breakpoints, the high-resolution multicolour banding (MCB) technique was applied to identify human chromosome 5 breakpoints from 40 clinical cases previously assessed by conventional banding techniques. In 30 cases (75%), at least one breakpoint was redefined, indicating that MCB markedly improves chromosomal breakpoint localisation. The MCB pattern is highly reproducible and, in contrast to conventional banding pattern, is consistent in both short and elongated chromosomes. This might be of fundamental interest for the detection of chromosomal abnormalities, especially in tumour cells. Moreover, MCB even allows the detection of abnormalities that remain cryptic in GTG-banding analysis.

Genomic imbalances in 61 renal cancers from the proximal tubulus detected by comparative genomic hybridization.

Comparative genomic hybridization (CGH) has been applied to characterize 61 primary renal cell carcinomas derived histogenetically from the proximal tubulus. The tumor samples comprised 46 clear-cell renal cell carcinomas (ccRCCs) and 15 papillary renal cell carcinomas (pRCCs). Changes in the copy number of entire chromosomes or subregions were detected in 56 tumors (92%). In ccRCCs, losses of chromosome 3 or 3p (63%); 14q (30%); 9 (26%); 1 and 6 or 6q (17% each); 4 and 8 or 8p (15% each); 22 (11%); 2 or 2q and 19 (9% each); 7q, 10, 16, 17p, 18, and Y (7% each); and 5, 11, 13, 15, and 21 (4% each) were detected. Most frequent genomic gains in ccRCC were found on chromosome 5 (63%); 7 (35%); 1 or 1q (33%); 2q (24%); 8 or 8q, 12, and 20 (20% each); 3q (17%); 16 (15%); 19 (13%); 6 and 17 or 17q (11% each); and 4, 10, 11, 21, and Y (9% each). In pRCCs, gains in the copy number of chromosomes 7 and 17 (7/15, each) and 16 and 20 (6/15, each) were frequent. One pRCC showed amplification of subchromosome regions 2q22-->q33, 16q, 17q and the entire X chromosome. In pRCC, losses were less frequently seen than gains. Losses of chromosomes 1, 14, 15, and Y (3/15 each) and 2, 4, 6, and 13 (2/15 each) were observed. In ccRCCs, statistical evaluation revealed significant correlations of chromosomal imbalances with tumor stage and grade, i.e., a gain in copy number of chromosome 5 correlated positively with low tumor grade, whereas a gain of chromosomes 10 and 17 correlated positively with high tumor grade. Furthermore, loss of chromosome 4 correlated positively with high tumor stage.

Comparative architectural aspects of regions of conserved synteny on human chromosome 11p15.3 and mouse chromosome 7 (including genes WEE1 and LMO1).

Human chromosome 11p15.3 is associated with chromosome aberrations in the Beckwith Wiedemann Syndrome and implicated in the pathogenesis of different tumor types including lung cancer and leukemias. To date, only single tumor-relevant genes with linkage to this region (e.g. LMO1) have been found suggesting that this region may harbor additional potential disease associated genes. Although this genomic area has been studied for years, the exact order of genes/chromosome markers between D11S572 and the WEE1 gene locus remained unclear. Using the FISH technique and PAC clones of the flanking markers we determined the order of the genomic markers. Based on these clones we established a PAC contig of the respective region. To analyse the chromosome area in detail the synteny of the orthologous region on distal mouse chromosome 7 was determined and a corresponding mouse clone contig established, proving the conserved order of the genes and markers in both species: "cen-WEE1-D11S2043-ZNF143-RANBP7-CEGF1- ST5-D11S932-LMO1-D11S572-TUB-tel", with inverted order of the murine genes with respect to the telomere/centromere orientation. The region covered by these contigs comprises roughly 1.6 MB in human as well as in mouse. The genomic sequence of the two subregions (around WEE1 and LMO1) in both species was determined using a shotgun sequencing strategy. Comparative sequence analysis techniques demonstrate that the content of repetitive elements seems to decline from centromere to telomere (52.6% to 34.5%) in human and in the corresponding murine region from telomere to centromere (41.87% to 27.82%). Genomic organisation of the regions around WEE1 and LMO1 was conserved, although the length of gene regions varied between the species in an unpredictable ratio. CpG islands were found conserved in putative promoter regions of the known genes but also in regions which so far have not been described as harboring expressed sequences.

Comparative genomic sequencing reveals a strikingly similar architecture of a conserved syntenic region on human chromosome 11p15.3 (including gene ST5) and mouse chromosome 7.

Comparative genomics is a superior way to identify phylogenetically conserved features like genes or regions involved in gene regulation. The comparison of extended orthologous chromosomal regions should also reveal other characteristic traits essential for chromosome or gene function. In the present study we have sequenced and compared a region of conserved synteny from human chromosome 11p15.3 and mouse chromosome 7. In human, this region is known to contain several genes involved in the development of various disorders like Beckwith-Wiedemann overgrowth syndrome and other tumor diseases. Furthermore, in the neighboring chromosome region 11p15.5 extensive imprinting of genes has been reported which might extend to region 11p15.3. The analysis of approximately 730 kb in human and 620 kb in mouse led to the identification of eleven genes. All putative genes found in the mouse DNA were also present in the same order and orientation in the human chromosome. However, in the human DNA one putative gene of unknown function could be identified which is not present in the orthologous position of the mouse chromosome. The sequence similarity between human and mouse is higher in transcribed and exon regions than in non-transcribed segments. Dot plot analysis, however, reveals a surprisingly well-conserved sequence similarity over the entire analyzed region. In particular, the positions of CpG islands, short regions of very high GC content in the 5' region of putative genes, are similar in human and mouse. With respect to base composition, two distinct segments of significantly different GC content exist as well in human as in the mouse. With a GC content of 45% the one segment would correspond to "isochore H1" and the other segment (39% GC in human, 40% GC in mouse) to "isochore L1/L2". The gene density (one gene per 66 kb) is slightly higher than the average calculated for the complete human genome (one gene per 90 kb). The comparison of the number and distribution of repetitive elements shows that the proportion of human DNA made up by interspersed repeats (43.8%) is significantly higher than in the corresponding mouse DNA (30.1%). This partly explains why the human DNA is longer between the landmark genes used to define the orthologous positions in human and mouse.

The molecular basis of X-linked spondyloepiphyseal dysplasia tarda.

The X-linked form of spondyloepiphyseal dysplasia tarda (SEDL), a radiologically distinct skeletal dysplasia affecting the vertebrae and epiphyses, is caused by mutations in the SEDL gene. To characterize the molecular basis for SEDL, we have identified the spectrum of SEDL mutations in 30 of 36 unrelated cases of X-linked SEDL ascertained from different ethnic populations. Twenty-one different disease-associated mutations now have been identified throughout the SEDL gene. These include nonsense mutations in exons 4 and 5, missense mutations in exons 4 and 6, small (2-7 bp) and large (>1 kb) deletions, insertions, and putative splicing errors, with one splicing error due to a complex deletion/insertion mutation. Eight different frameshift mutations lead to a premature termination of translation and account for >43% (13/30) of SEDL cases, with half of these (7/13) being due to dinucleotide deletions. Altogether, deletions account for 57% (17/30) of all known SEDL mutations. Four recurrent mutations (IVS3+5G-->A, 157-158delAT, 191-192delTG, and 271-275delCAAGA) account for 43% (13/30) of confirmed SEDL cases. The results of haplotype analyses and the diverse ethnic origins of patients support recurrent mutations. Two patients with large deletions of SEDL exons were found, one with childhood onset of painful complications, the other relatively free of additional symptoms. However, we could not establish a clear genotype/phenotype correlation and therefore conclude that the complete unaltered SEDL-gene product is essential for normal bone growth. Molecular diagnosis can now be offered for presymptomatic testing of this disorder. Appropriate lifestyle decisions and, eventually, perhaps, specific SEDL therapies may ameliorate the prognosis of premature osteoarthritis and the need for hip arthroplasty.

Regulation of glomerular basement membrane collagen expression by LMX1B contributes to renal disease in nail patella syndrome.

Basement membrane (BM) morphogenesis is critical for normal kidney function. Heterotrimeric type IV collagen, composed of different combinations of six alpha-chains (1-6), is a major matrix component of all BMs (ref. 2). Unlike in other BMs, glomerular BM (GBM) contains primarily the alpha 3(IV) and alpha 4(IV) chains, together with the alpha 5(IV) chain. A poorly understood, coordinated temporal and spatial switch in gene expression from ubiquitously expressed alpha 1(IV) and alpha 2(IV) collagen to the alpha 3(IV), alpha 4(IV) and alpha 5(IV) chains occurs during normal embryogenesis of GBM (ref. 4). Structural abnormalities of type IV collagen have been associated with diverse biological processes including defects in molecular filtration in Alport syndrome, cell differentiation in hereditary leiomyomatosis, and autoimmunity in Goodpasture syndrome; however, the transcriptional and developmental regulation of type IV collagen expression is unknown. Nail patella syndrome (NPS) is caused by mutations in LMX1B, encoding a LIM homeodomain transcription factor. Some patients have nephrosis-associated renal disease characterized by typical ultrastructural abnormalities of GBM (refs. 8,9). In Lmx1b(-/-) mice, expression of both alpha(3)IV and alpha(4)IV collagen is strongly diminished in GBM, whereas that of alpha1, alpha2 and alpha5(IV) collagen is unchanged. Moreover, LMX1B binds specifically to a putative enhancer sequence in intron 1 of both mouse and human COL4A4 and upregulates reporter constructs containing this enhancer-like sequence. These data indicate that LMX1B directly regulates the coordinated expression of alpha 3(IV) and alpha 4(IV) collagen required for normal GBM morphogenesis and that its dysregulation in GBM contributes to the renal pathology and nephrosis in NPS.