An inverse correlation between expression of a preprocathepsin B-related protein with cysteine-rich sequences and steroid 11beta -hydroxylase in adrenocortical cells

Tubulointerstitial nephritis antigen-like 1 from cancer-associated fibroblasts contribute to the progression of diffuse-type gastric cancers through the interaction with integrin β1

BACKGROUND

Tumor cells of diffuse-type gastric cancer (DGC) are discohesive and infiltrate into the stroma as single cells or small subgroups, so the stroma significantly impacts DGC progression. Cancer-associated fibroblasts (CAFs) are major components of the tumor stroma. Here, we identified CAF-specific secreted molecules and investigated the mechanism underlying CAF-induced DGC progression.

METHODS

We conducted transcriptome analysis for paired normal fibroblast (NF)-CAF isolated from DGC patient tissues and proteomics for conditioned media (CM) of fibroblasts. The effects of fibroblasts on cancer cells were examined by transwell migration and soft agar assays, western blotting, and in vivo. We confirmed the effect of blocking tubulointerstitial nephritis antigen-like 1 (TINAGL1) in CAFs using siRNA or shRNA. We evaluated the expression of TINAGL1 protein in frozen tissues of DGC and paired normal stomach and mRNA in formalin-fixed, paraffin-embedded (FFPE) tissue using RNA in-situ hybridization (RNA-ISH).

RESULTS

CAFs more highly expressed TINAGL1 than NFs. The co-culture of CAFs increased migration and tumorigenesis of DGC. Moreover, CAFs enhanced the phosphorylation of focal adhesion kinase (FAK) and mesenchymal marker expression in DGC cells. In an animal study, DGC tumors co-injected with CAFs showed aggressive phenotypes, including lymph node metastasis. However, increased phosphorylation of FAK and migration were reduced by blocking TINAGL1 in CAFs. In the tissues of DGC patients, TINAGL1 was higher in cancer than paired normal tissues and detected with collagen type I alpha 1 chain (COL1A1) in the same spot. Furthermore, high TINAGL1 expression was significantly correlated with poor prognosis in several public databases and our patient cohort diagnosed with DGC.

CONCLUSIONS

These results indicate that TINAGL1 secreted by CAFs induces phosphorylation of FAK in DGC cells and promotes tumor progression. Thus, targeting TINAGL1 in CAFs can be a novel therapeutic strategy for DGC.

Functional analysis reveals that Tinagl1 is required for normal muscle development in mice through the activation of ERK signaling

Tinagl1 (tubulointerstitial nephritis antigen-like 1) is a matricellular protein involved in female infertility and breast cancer tumorigenesis. In this study, we analyzed the function of Tinagl1 in skeletal muscle using knockout mice and cell experiments. Although primary myoblasts isolated from Tinagl1-decifient (Tinagl1^-/-) mice differentiated into normal myotubes, and treatment with recombinant Tinagl1 did not affect the proliferation or differentiation of C2C12 myoblasts, Tinagl1^-/- mice exhibited reduced body mass and calf muscle weights compared to the control group (Tinagl1^flox/flox). Furthermore, Tinagl1^-/- mice showed myofibers with centrally located nuclei, which is a morphological marker of regenerating muscle or myopathy. In addition, the capillary density in the soleus muscle of Tinagl1^-/- mice showed a decreasing trend compared to that of the control group. Importantly, si-RNA-mediated knockdown of TINAGL1 resulted in reduced tube formation in human umbilical vein endothelial cells (HUVECs), whereas treatment with Tinagl1 promoted tube formation. Immunoblot analysis revealed that Tinagl1 activates ERK signaling in both HUVECs and C2C12 myoblasts and myotubes, which are involved in the regulation of myogenic differentiation, proliferation, metabolism, and angiogenesis. Our results demonstrate that Tinagl1 may be required for normal muscle and capillary development through the activation of ERK signaling.

Down-regulated TINAGL1 in fibroblasts impairs wound healing in diabetes

Matricellular proteins, a group of extracellular matrix (ECM) proteins, are key regulators of skin repair and their dysregulation impairs wound healing in diabetes. Tubulointerstitial nephritis antigen like 1 (TINAGL1) is a new member of matricellular protein family, and the understanding of its functional role is still relatively limited. In the current study, we detected the expression of TINAGL1 in diabetic skin wound tissues through RT-PCR, ELISA and Western blot analysis, investigated the contribution of TINAGL1 to wound healing through cutaneous administration of recombinant TINAGL1 protein, and characterized its regulation by hyperglycemia through RNA-seq and signal pathway inhibition assay. We showed that TINAGL1 expression has dynamic change and reaching a peak on day-9 after wound during the wound healing process in wild-type (WT) mice. Interestingly, decreased TINAGL1 expression is detected in skin tissues of diabetic patients and mice after wound. Then, we found that high glucose (HG), an important factor that impairs wound healing, reduces the expression of TINAGL1 in fibroblasts through JNK pathway. Notably, the histology analysis, Masson trichrome assay and IHC assay showed that exogenous TINAGL1 promotes wound healing in diabetic mice by accelerating the formation of granulation tissues. Our study provides evidence that TINAGL1 has an essential role in diabetic wound healing, and meanwhile, indicates that manipulation of TINAGL1 might be a possible therapeutic approach.

Early Craniofacial Defects in Zebrafish that Have Reduced Function of a Wnt-Interacting Extracellular Matrix Protein, Tinagl1

Objective

Tinagl1 has a weak genetic association with craniosynostosis, but its functions in cartilage and bone development are unknown. Knockdown of Tinagl1 in zebrafish embryos allowed an initial characterization of its potential effects on craniofacial cartilage development and a test of whether these effects could involve Wnt signaling.

Results

Tinagl1 knockdown resulted in dose-dependent reductions and defects in ventral pharyngeal arch cartilages as well as the ethmoid plate, a zebrafish correlate to the palate. These defects could be correlated to reduced numbers of cranial neural crest cells in the pharyngeal arches and could be reproduced with comanipulation of Tinagl1 and Wnt3a by morpholino-based knockdown.

Conclusions

These results suggest that Tinagl1 is required early in the proliferation or migration of cranial neural crest cells and that its effects are mediated via Wnt3a signaling. Because Wnt3a is among the Wnts that contribute to nonsyndromic cleft lip and cleft palate in mouse and man, further investigation of Tinagl1 may help to elucidate mechanisms underlying these disorders.

Molecular and cellular events during blastocyst implantation in the receptive uterus: clues from mouse models

The success of implantation is an interactive process between the blastocyst and the uterus. Synchronized development of embryos with uterine differentiation to a receptive state is necessary to complete pregnancy. The period of uterine receptivity for implantation is limited and referred to as the “implantation window”, which is regulated by ovarian steroid hormones. Implantation process is complicated due to the many signaling molecules in the hierarchical mechanisms with the embryo-uterine dialogue. The mouse is widely used in animal research, and is uniquely suited for reproductive studies, i.e., having a large litter size and brief estrous cycles. This review first describes why the mouse is the preferred model for implantation studies, focusing on uterine morphology and physiological traits, and then highlights the knowledge on uterine receptivity and the hormonal regulation of blastocyst implantation in mice. Our recent study revealed that selective proteolysis in the activated blastocyst is associated with the completion of blastocyst implantation after embryo transfer. Furthermore, in the context of blastocyst implantation in the mouse, this review discusses the window of uterine receptivity, hormonal regulation, uterine vascular permeability and angiogenesis, the delayed-implantation mouse model, morphogens, adhesion molecules, crosslinker proteins, extracellular matrix, and matricellular proteins. A better understanding of uterine and blastocyst biology during the peri-implantation period should facilitate further development of reproductive technology.

Functional Zonation of the Adult Mammalian Adrenal Cortex

The standard model of adrenocortical zonation holds that the three main zones, glomerulosa, fasciculata, and reticularis each have a distinct function, producing mineralocorticoids (in fact just aldosterone), glucocorticoids, and androgens respectively. Moreover, each zone has its specific mechanism of regulation, though ACTH has actions throughout. Finally, the cells of the cortex originate from a stem cell population in the outer cortex or capsule, and migrate centripetally, changing their phenotype as they progress through the zones. Recent progress in understanding the development of the gland and the distribution of steroidogenic enzymes, trophic hormone receptors, and other factors suggests that this model needs refinement. Firstly, proliferation can take place throughout the gland, and although the stem cells are certainly located in the periphery, zonal replenishment can take place within zones. Perhaps more importantly, neither the distribution of enzymes nor receptors suggest that the individual zones are necessarily autonomous in their production of steroid. This is particularly true of the glomerulosa, which does not seem to have the full suite of enzymes required for aldosterone biosynthesis. Nor, in the rat anyway, does it express MC2R to account for the response of aldosterone to ACTH. It is known that in development, recruitment of stem cells is stimulated by signals from within the glomerulosa. Furthermore, throughout the cortex local regulatory factors, including cytokines, catecholamines and the tissue renin-angiotensin system, modify and refine the effects of the systemic trophic factors. In these and other ways it more and more appears that the functions of the gland should be viewed as an integrated whole, greater than the sum of its component parts.

Impaired female fertility in tubulointerstitial antigen-like 1-deficient mice

Tubulointerstitial nephritis antigen-like 1 (Tinagl1, also known as adrenocortical zonation factor 1 [AZ-1] or lipocalin 7) is a matricellular protein. Previously, we demonstrated that Tinagl1 expression was restricted to extraembryonic regions during the postimplantation period and detected marked expression in mouse Reichert's membranes. In uteri, Tinagl1 is markedly expressed in the decidual endometrium during the postimplantation period, suggesting that it plays a physical and physiological role in embryo development and/or decidualization of the uterine endometrium during pregnancy. In the present study, in order to determine the role of Tinagl1 during embryonic development and pregnancy, we generated Tinagl1-deficient mice. Although Tinagl1(-/-) embryos were not lethal during development to term, homologous matings of Tinagl1(-/-) females and Tinagl1(-/-) males showed impaired fertility during pregnancy, including failure to carry pregnancy to term and perinatal lethality. To examine ovarian function, ovulation was induced with equine chorionic gonadotropin (eCG) and human chorionic gonadotropin (hCG); the number of ovulated oocytes did not differ between Tinagl1(-/-) and Tinagl1(flox/flox). In vitro fertilization followed by embryo culture also demonstrated the normal developmental potential of Tinagl1-null embryos during the preimplantation period. Our results demonstrate that Tinagl1 deficiency affects female mice and results in subfertility phenotypes, and they suggest that although the potential of Tinagl1(-/-) oocytes is normal, Tinagl1 is related to fertility in adult females but is not essential for either fertilization or preimplantation development in vitro.

Molecular and cellular events involved in the completion of blastocyst implantation

Blastocyst implantation is an interactive process between the embryo and the uterus. The synchronization of embryonic development with uterine differentiation to a receptive state is essential for a successful pregnancy. The period of uterine receptivity for implantation is limited. Although implantation involves the interaction of numerous signaling molecules, our understanding of the hierarchical mechanisms that coordinate with the embryo-uterine dialogue is not yet sufficient to prevent infertility caused by implantation failure. This review highlights our knowledge on uterine receptivity and hormonal regulation of blastocyst implantation in mice. We also discuss the adhesion molecules, cross-linker proteins, extracellular proteins, and matricellular proteins involved in blastocyst implantation. Furthermore, our recent study reveals that selective proteolysis in an activated blastocyst is associated with the completion of blastocyst implantation after embryo transfer. A better understanding of uterine and blastocyst biology during the peri-implantation period would facilitate further development of reproductive technology.

Laser capture microdissection-reduced representation bisulfite sequencing (LCM-RRBS) maps changes in DNA methylation associated with gonadectomy-induced adrenocortical neoplasia in the mouse

DNA methylation is a mechanism for long-term transcriptional regulation and is required for normal cellular differentiation. Failure to properly establish or maintain DNA methylation patterns leads to cell dysfunction and diseases such as cancer. Identifying DNA methylation signatures in complex tissues can be challenging owing to inaccurate cell enrichment methods and low DNA yields. We have developed a technique called laser capture microdissection-reduced representation bisulfite sequencing (LCM-RRBS) for the multiplexed interrogation of the DNA methylation status of cytosine–guanine dinucleotide islands and promoters. LCM-RRBS accurately and reproducibly profiles genome-wide methylation of DNA extracted from microdissected fresh frozen or formalin-fixed paraffin-embedded tissue samples. To demonstrate the utility of LCM-RRBS, we characterized changes in DNA methylation associated with gonadectomy-induced adrenocortical neoplasia in the mouse. Compared with adjacent normal tissue, the adrenocortical tumors showed reproducible gains and losses of DNA methylation at genes involved in cell differentiation and organ development. LCM-RRBS is a rapid, cost-effective, and sensitive technique for analyzing DNA methylation in heterogeneous tissues and will facilitate the investigation of DNA methylation in cancer and organ development.

Distribution of tubulointerstitial nephritis antigen-like 1 and structural matrix proteins in mouse embryos during preimplantation development in vivo and in vitro

Tubulointerstitial nephritis antigen-like 1 (TINAGL1) is a novel matricellular protein that interacts with structural matrix proteins and promotes cell adhesion and spreading. We have previously reported unique localization of TINAGL1 to the trophectoderm (TE) of mouse blastocysts. TINAGL1 was found to be upregulated in implantation-competent blastocysts after estrogen treatment using progesterone-treated delayed-implantation models. Moreover, colocalization of TINAGL1 and extracellular matrix (ECM) protein laminin 1 was detected in the Reichert membrane on embryonic days 6.5 and 7.5. Although these data suggested a role for TINAGL1 in the embryo development at postimplantation, its relevance to other ECM proteins during preimplantation development is not clear. In this study, we examined the expression of TINAGL1 and its relevance to other ECM proteins fibronectin (FN) and collagen type IV (ColIV) during in vivo development of preimplantation embryos, particularly at blastocyst stage in detail. Localizations of TINAGL1, FN, and ColIV were similar. In 1-cell to 8-cell embryos, they were expressed in cytoplasm of blastomeres, and in morulae they were localized in the outer cells. FN and ColIV were expressed primarily on outer surface of the cells. In blastocysts, FN and ColIV were distributed in the cytoplasm of TE, but, just prior to implantation, they became localized uniquely to the blastocoelic surface of TE. In in vitro fertilized (IVF) blastocysts, expression levels of TINAGL1 and FN were lower than in in vivo blastocysts. These results suggest that, during preimplantation development, TINAGL1 may be involved in roles of structural matrix proteins, whose expression in blastocysts may be affected by in vitro culture.

Transcriptome analysis reveals differentially expressed transcripts in rat adrenal zona glomerulosa and zona fasciculata

In mammals, aldosterone is produced in the zona glomerulosa (zG), the outermost layer of the adrenal cortex, whereas glucocorticoids are produced in adjacent zona fasciculata (zF). However, the cellular mechanisms controlling the zonal development and the differential hormone production (i.e. functional zonation) are poorly understood. To explore the mechanisms, we defined zone-specific transcripts in this study. Eleven-week-old male rats were used and adrenal tissues were collected from zG and zF using laser-capture microdissection. RNA was isolated, biotin labeled, amplified, and hybridized to Illumina microarray chips. The microarray data were compared by fold change calculations. In zG, 235 transcripts showed more than a 2-fold up-regulation compared to zF with statistical significance. Similarly, 231 transcripts showed up-regulation in zF. The microarray findings were validated using quantitative RT-PCR and immunohistochemical staining on selected transcripts, including Cyp11b2 (zG/zF: 214.2x), Rgs4 (68.4x), Smoc2 (49.3x), and Mia1 (43.1x) in zG as well as Ddah1 (zF/zG 16.2x), Cidea (15.5x), Frzb (9.5x), and Hsd11b2 (8.3x) in zF. The lists of transcripts obtained in the current study will be an invaluable tool for the elucidation of cellular mechanisms leading to zG and zF functional zonation.

Lipocalin-7 is a matricellular regulator of angiogenesis

BACKGROUND

Matricellular proteins are extracellular regulators of cellular adhesion, signaling and performing a variety of physiological behaviors such as proliferation, migration and differentiation. Within vascular microenvironments, matricellular proteins exert both positive and negative regulatory cues to vascular endothelium. The relative balance of these matricellular cues is believed to be critical for vascular homeostasis, angiogenesis activation or angiogenesis resolution. However, our knowledge of matricellular proteins within vascular microenvironments and the mechanisms by which these proteins impact vascular function remain largely undefined. The matricellular protein lipocalin-7 (LCN7) is found throughout vascular microenvironments, and circumstantial evidence suggests that LCN7 may be an important regulator of angiogenesis. Therefore, we hypothesized that LCN7 may be an important regulator of vascular function.

METHODOLOGY AND PRINCIPAL FINDINGS

To test this hypothesis, we examined the effect of LCN7 overexpression, recombinant protein and gene knockdown in a series of in vitro and in vivo models of angiogenesis. We found that overexpression of LCN7 in MB114 and SVEC murine endothelial cell lines or administration of highly purified recombinant LCN7 protein increased endothelial cell invasion. Similarly, LCN7 increased angiogenic sprouting from quiescent endothelial cell monolayers and ex vivo aortic rings. Moreover, LCN7 increased endothelial cell sensitivity to TGF-β but did not affect sensitivity to other pro-angiogenic growth factors including bFGF and VEGF. Finally, morpholino based knockdown of LCN7 in zebrafish embryos specifically inhibited angiogenic sprouting but did not affect vasculogenesis within injected embryos.

CONCLUSIONS AND SIGNIFICANCE

No functional analysis has previously been performed to elucidate the function of LCN7 in vascular or other cellular processes. Collectively, our results show for the first time that LCN7 is an important pro-angiogenic matricellular protein of vascular microenvironments.

Tubulointerstitial nephritis antigen-like 1 is expressed in the uterus and binds with integrins in decidualized endometrium during postimplantation in mice

Extracellular matrix substrates contribute to both uterine and blastocyst functions during the peri-implantation period. Tubulointerstitial nephritis antigen-like 1 (TINAGL1, also known as adrenocortical zonation factor 1 [AZ-1] or lipocalin 7) is a novel matricellular protein that promotes cell adhesion and spreading. However, the physiological roles of TINAGL1 are still not clearly understood. We examined the expression and localization of TINAGL1 in peri-implantation mouse uteri. During the preimplantation period, TINAGL1 was expressed in the basement membranes of uterine luminal epithelial cells on Days 1 and 2 of pregnancy, while its expression levels declined after Day 3. In the whole uteri, the expression levels of Tinagl1 mRNA and TINAGL1 protein were similar on Days 1-4 of pregnancy. In contrast, the expression of Tinagl1 mRNA and TINAGL1 protein increased in postimplantation uteri. From Days 6 to 8, TINAGL1 was markedly expressed in the decidual endometrium. TINAGL1 is a ligand for integrins and promotes cell adhesion in cultured cells. Therefore, to address whether TINAGL1 interacts with integrins in the uterus, immunohistochemical analysis and immunoprecipitation were performed. Immunohistochemical analysis showed that ITGA2, ITGA5, and ITGB1 were expressed in stromal cells around the implanted embryos on Days 7 and 8. Biacore and immunoprecipitation analysis determined that TINAGL1 linked with ITGA5 and ITGB1 in the decidual endometrium. These results suggest that Tinagl1 functions during the postimplantation period; in particular, it associates with ITGA5B1 in the decidualized uterine endometrium.

Tubulointerstitial nephritis antigen-like 1 is expressed in extraembryonic tissues and interacts with laminin 1 in the Reichert membrane at postimplantation in the mouse

Tubulointerstitial nephritis antigen-like 1 (Tinagl1, also known as adrenocortical zonation factor 1 [AZ-1] or lipocalin 7) has been cloned from mouse adrenocortical cells and is known to be closely associated with zonal differentiation of adrenocortical cells. In cell culture systems, TINAGL1 is a matricellular protein that interacts with both structural matrix proteins and cell surface receptors. However, the physiological roles of TINAGL1 and regulation of its expression are still not clearly understood. In the present study, the expression and localization of TINAGL1 in peri-implantation mouse embryos was examined. During preimplantation, the expression of both Tinagl1 mRNA and TINAGL1 protein was increased just prior to implantation. In blastocysts, TINAGL1 expression was localized to the trophectoderm. Using a progesterone-treated, delayed-implantation model, TINAGL1 was found to be upregulated in implantation-competent blastocysts after estrogen treatment. During postimplantation, TINAGL1 expression was restricted to extraembryonic regions. Marked expression was detected in the Reichert membrane on Embryonic Days 6.5 (E6.5) and E7.5. Colocalization of laminin 1 and TINAGL1 was also examined. Using an anti-LAMA1 antibody, colocalization of LAMA1 and TINAGL1 was observed in postimplantation embryos. Colocalization was also detected in the Reichert membrane. Immunoprecipitation analysis determined that LAMA1 and TINAGL1 interact in embryos on E7.5. These results demonstrate that after implantation, TINAGL1 is an extraembryonic tissue-specific protein. In particular, TINAGL1 is a novel component of the Reichert membrane that interacts with laminin 1. These results suggest that TINAGL1 most likely plays a physical and physiological role in embryo development at postimplantation.

Adrenocortical zonation factor 1 is a novel matricellular protein promoting integrin-mediated adhesion of adrenocortical and vascular smooth muscle cells

Expression of a previously cloned secretory protein named adrenocortical zonation factor 1 (AZ-1, also called Tin-ag-RP or lipocalin 7) is tightly linked with the zonal differentiation of adrenocortical cells. It is also present in vascular smooth muscle (VSM), although its function has remained unknown. In this study, the location of AZ-1 was specified to the basal laminae along adrenocortical sinusoidal capillaries and surrounding VSM cells in the arterial system, consistent with the fact that AZ-1 was extractable under denaturing conditions as a 52 kDa polypeptide. Purified recombinant AZ-1 exhibited abilities to bind to fibronectins via the first type III repeat (anastellin) and to collagens with affinities in submicromolar ranges. AZ-1 immobilized on substratum or bound to collagens or anastellin promoted adhesion and spreading of adrenocortical cells. Although VSM cells spread on AZ-1 slowly, AZ-1 bound to anastellin facilitated the spreading. The adhesion activity of AZ-1 was mediated by a subset of integrins, including alpha(1)beta(1), alpha(2)beta(1), and alpha(5)beta(1), in a cell type-specific manner. Collectively with the putative role of AZ-1 in the adrenocortical zonation, we propose that AZ-1 potentially regulates functions of adrenocortical and VSM cells by modulating cell-matrix interactions.

Minor proteins and enzymes of the Drosophila eggshell matrix

The Drosophila eggshell provides an in vivo model system for extracellular matrix assembly, in which programmed gene expression, cell migrations, extracellular protein trafficking, proteolytic processing, and cross-linking are all required to generate a multi-layered and regionally complex architecture. While abundant structural components of the eggshell are known and are being characterized, less is known about non-abundant structural, regulatory, and enzymatic components that are likely to play critical roles in eggshell assembly. We have used sensitive mass spectrometry-based analyses of fractionated eggshell matrices to validate six previously predicted eggshell proteins and to identify eleven novel components, and have characterized the expression patterns of many of their mRNAs. Among these are several putative structural or regulatory (non-enzymatic) proteins, most larger in mass than the major eggshell proteins and often showing preferential expression in follicle cells overlying specific structural features of the eggshell. Of particular note are the putative enzymes, some likely to be involved in matrix cross-linking (two yellow family members previously implicated in eggshell integrity, a heme peroxidase, and a small-molecule oxidoreductase) and others possibly involved in matrix proteolysis or adhesion (proteins related to cathepsins B and D). This work provides a framework for future molecular studies of eggshell assembly.

Corticosteroid-regulated genes in rat kidney: mining time series array data

Kidney is a major target for adverse effects associated with corticosteroids. A microarray dataset was generated to examine changes in gene expression in rat kidney in response to methylprednisolone. Four control and 48 drug-treated animals were killed at 16 times after drug administration. Kidney RNA was used to query 52 individual Affymetrix chips, generating data for 15,967 different probe sets for each chip. Mining techniques applicable to time series data that identify drug-regulated changes in gene expression were applied. Four sequential filters eliminated probe sets that were not expressed in the tissue, not regulated by drug, or did not meet defined quality control standards. These filters eliminated 14,890 probe sets (94%) from further consideration. Application of judiciously chosen filters is an effective tool for data mining of time series datasets. The remaining data can then be further analyzed by clustering and mathematical modeling. Initial analysis of this filtered dataset identified a group of genes whose pattern of regulation was highly correlated with prototype corticosteroid enhanced genes. Twenty genes in this group, as well as selected genes exhibiting either downregulation or no regulation, were analyzed for 5' GRE half-sites conserved across species. In general, the results support the hypothesis that the existence of conserved DNA binding sites can serve as an important adjunct to purely analytic approaches to clustering genes into groups with common mechanisms of regulation. This dataset, as well as similar datasets on liver and muscle, are available online in a format amenable to further analysis by others.

Neonatal salt-wasting and 11 β-hydroxylase deficiency in a child carrying a homozygous deletion hybrid CYP11B2 (aldosterone synthase)-CYP11B1 (11 β-hydroxylase)

This article reports the case of a boy diagnosed at 1.8 years of age with congenital adrenal hyperplasia due to 11 beta-hydroxylase deficiency. The patient showed salt-wasting episodes during the neonatal period. On molecular analysis, a homozygous deletion hybrid (CYP11B2-CYP11B1) involving the CYP11B locus at 8q24.3 was found. Southern blot analysis showed the break point of the chimera gene to be located before intron 5; sequence analysis identified it at exon 4 between codons 202 and 248. This CYP11B2(5')/B1(3') hybrid should lack aldosterone synthase activity (due to the CYP11B1 residues at exons 5 and 6), and the enzyme it codes for should not be promoted by adrenocorticotropic hormone (ACTH) (CYP11B2 promoter sequences). The patient phenotype - neonatal salt-wasting and 11 beta-hydroxylase deficiency - is in agreement with this hybrid structure. This is the first time a homozygous deletion hybrid generated by unequal crossover has been described in exon 4. This genetic lesion appears to be the reciprocal product from the recombination event that causes glucocorticoid-remediable aldosteronism, a duplication dominant allele (CYP11B2-CYP11B1/B2-CYP11B1) coding for additional aldosterone synthase activity regulated by ACTH. The clinical presentation of the condition in this patient contributes to the in vivo understanding of the regulation of this complex locus in which two 'duplicated' genes have evolved different regulatory and enzymatic activities involved in mineralocorticoid and glucocorticoid synthesis in the adrenal glands. The fact that this allele was first predicted and has now been documented clinically and molecularly in vivo is particularly noteworthy.

Characterization of the adrenal-specific antigen IZA (inner zone antigen) and its role in the steroidogenesis

Inner zone antigen (IZA) is a protein specifically expressed in the zona fasciculata and reticularis of the adrenal cortex. The cDNA encoding IZA was found to be identical to that encoding the previously reported putative membrane-associated progesterone receptor (MPR) and the TCDD-induced 25kDa protein (25-Dx). From its structure, MPR was classed as a member of a protein family containing a haem-binding domain, and progesterone was proposed to be a ligand of this domain. Indeed, when GST-tagged IZA was expressed in Escherichia coli and purified, the purified GST-IZA had a brown colour with maximum absorbance at 400 nm. The addition of dithionate shifted the absorbance peak to 420 nm, suggesting a haem-binding function. The possible role of IZA in steroidogenesis has been addressed, and the inhibition of adrenal steroidogenesis by the addition of an anti-IZA monoclonal antibody has been reported. When COS-7 cells were transformed with plasmids for appropriate steroidogenic enzymes in the presence or absence of an IZA expression plasmid and tested for their steroidogenic activities, 21-hydroxylation of progesterone was found to be specifically activated by IZA overexpression, suggesting the involvement of IZA in progesterone metabolism. Taken together, the available evidence suggests that IZA may have an important role in the functions of the adrenal zona fasciculata and reticularis.