Expression profile of Papss2 (3'-phosphoadenosine 5'-phosphosulfate synthase 2) during cartilage formation and skeletal development in the mouse embryo.

Sulfation of proteoglycans is a very important posttranslational modification in chondrocyte growth and development. The enzyme 3'-phosphoadenosine 5'-phosphosulfate synthase (PAPSS) catalyzes the biosynthesis of PAPS (3'-phosphoadenosine 5'-phosphosulfate), which serves as the universal sulfate donor compound for all sulfotransferase reactions (Schwartz and Domowicz [2002] Glycobiology 109:143-151). Two major isoenzymes, PAPS synthase 1 (PAPSS1) and PAPS synthase 2 (PAPSS2) were identified in higher organisms for the synthesis of PAPS. PAPSS1 is the more prominent isoform and is ubiquitously expressed in human adult tissues, including cartilage, while PAPSS2 shows a more restricted expression pattern and appears to be the major variant in growth plate cartilage (Fuda et al. [2002] Biochem J 365(Pt 2):497-504). Mutations within the murine and the human PAPSS2 genes are responsible for diseases affecting the skeletal system (Kurima et al. [1998] Proc Natl Acad Sci USA 95:8681-8685; ul Haque et al. [1998] Nat Genet 20:157-162), like the spondyloepimetaphyseal dysplasia (SEMD) Pakistani type. To further elucidate the function of Papss2 within the developing skeleton, we investigated the expression pattern of the murine gene at different developmental stages. We detected Papss2 mRNA starting from 11.5 days post coitum (dpc) at the sites of first chondrogenic condensations and the expression continued in all cartilaginous elements tested of 12.5 dpc, 13.5 dpc, 16.5 dpc embryos, and newborn mice. Papss2 transcripts were also observed in other tissues such as heart, tongue, kidney, and neuronal tissues. However, the most significant levels of Papss2 mRNA were found in condensing and proliferating chondrocytes, whereas hypertrophic chondrocytes show a dramatic down-regulation of Papss2 mRNA expression, indicating an important role of the gene product for cartilage growth and development in mouse embryo.

Expression profiling of human fetal growth plate cartilage by EST sequencing.

The differentiation of mesenchymal stem cells into hypertrophic chondrocytes is an integral and multistep process important in pattern formation, endochondral ossification, and postnatal growth of the skeleton. In recent years, novel genes involved in these processes have been identified, but still only little is known about the large-scale gene expression profile during skeletal development. We initiated an expressed sequence tag (EST) project aiming at the identification of genes and pathways involved in this complex process. Candidate genes are expected to be of value for diagnosis and treatment of monogenic and multigenic heritable disorders of the skeleton. Here, we describe the sequences of 4,748 clones from a human growth plate cartilage cDNA library generated from 20 weeks prenatal-2 years postnatal specimens. In silico analysis of these sequences revealed 1,688 individual transcription units, corresponding to known (1,274) and to novel, yet uncharacterised potential genes (414). The tissue specificity of the library was reflected by its corresponding EST profile representing a total of approximately 10% proteins already shown to be involved in cartilage/bone development or homeostasis. The EST profile also reflects the developmental stage of the tissue with significant differences in the expression of matrix proteins compared to corresponding EST profiles from 8-12 and 12-20 week human fetal cartilage. Calculation of the relative frequency of transcripts in our cDNA library, as compared to their abundance in other EST datasets, revealed a set of approximately 200 genes, including 81 novel, yet uncharacterised genes, showing increased expression. These genes represent candidates for the large number of osteochondrodysplasias for which the causative gene defects have not yet been identified.

SPOC1, a novel PHD-finger protein: association with residual disease and survival in ovarian cancer.

We report the identification of a novel human gene (SPOC1) which encodes a protein with a PHD-finger domain. The gene is located in chromosomal region 1p36.23, a region implicated in tumor development and progression. RNA in situ hybridization experiments showed strong SPOC1 expression in some rapidly proliferating cell types, such as spermatogonia, but not in nonproliferating mature spermatocytes. In addition, high SPOC1 mRNA expression was observed in several ovarian cancer cell lines. This prompted us to systematically examine SPOC1 expression in ovarian cancer in relation to prognosis. SPOC1 mRNA expression was quantified in tumor tissue of 103 patients with epithelial ovarian cancer. Interestingly, SPOC1 was associated with residual disease, whereby patients with unresectable tumors showed higher levels compared to patients without residual tumor tissue after surgery (p = 0.029). The univariable proportional hazards model showed an association between SPOC1 expression and survival (p = 0.043, relative risk = 1.535). Median survival time was 1,596 days for patients with low SPOC1 expression vs. only 347 days for patients with high expression, using Kaplan-Meier analysis. However, SPOC1 was not associated with survival when multivariable analysis was adjusted for residual disease. This can be explained by the correlation between residual disease and SPOC1 expression. In conclusion, SPOC1 is a novel PHD-finger protein showing strong expression in spermatogonia and ovarian cancer cells. SPOC1 overexpression was associated with unresectable carcinomas and shorter survival in ovarian cancer.

Grebe dysplasia and the spectrum of CDMP1 mutations.

We report on a 4-year-old boy with the typical phenotype of Grebe dysplasia born to consanguineous parents. The father seems to be unaffected; the mother presents with brachydactyly type C (BdC). PCR amplification and sequencing of the cartilage-derived morphogenetic protein 1 (CDMP1) gene of the parents led to the identification of a heterozygous insertion of a single G at nucleotide 206. The mutation that causes frameshift and premature termination is predicted to result in functional haploinsufficiency. The child is homozygous for the insertion (insG206). The phenotypic spectrum of this loss-of-function mutation ranges from normal or BdC in heterozygotes to Grebe-type chondrodysplasia in the homozygously affected and seems to be due to CDMP1 gradient effects during pattern formation. A dominant negative action on other bone morphogenetic proteins is unlikely to cause the severe disruption of skeletogenesis seen in this case of Grebe dysplasia.