Growth factors FGF8 and FGF2 and their receptor FGFR1, transcriptional factors Msx-1 and MSX-2, and apoptotic factors p19 and RIP5 participate in the early human limb development

Msx1-Modified Rat Bone Marrow Mesenchymal Stem Cell Therapy for Rotator Cuff Repair: A Comprehensive Analysis of Tendon-Bone Healing and Cellular Mechanisms

This study investigates the therapeutic potential of Msx1-overexpressing bone marrow mesenchymal stem cells (BMSCs) in enhancing tendon-bone healing in rotator cuff injuries. BMSCs were genetically modified to overexpress Msx1 and were evaluated in vitro for their proliferation, migration, and differentiation potential. Results demonstrated that Msx1 overexpression significantly increased BMSC proliferation and migration while inhibiting osteogenic and chondrogenic differentiation. In a rat model of acute rotator cuff injury, Msx1-BMSCs embedded in a hydrogel scaffold were implanted at the tendon-bone junction. Micro-CT analysis revealed substantial new bone formation in the Msx1-BMSC group, and histological evaluation showed organized collagen and cartilage structures at the repair site. Biomechanical testing further confirmed enhanced structural strength in the Msx1-BMSC-treated group. These findings suggest that Msx1 modification enhances BMSC-mediated repair by promoting cell proliferation and migration, facilitating tendon-bone integration. This Msx1-based approach presents a promising strategy for advancing regenerative therapies for rotator cuff injuries.

The Complexity and Significance of Fibroblast Growth Factor (FGF) Signaling for FGF-Targeted Cancer Therapies

Fibroblast growth factors (FGFs) have diverse functions in the regulation of cell proliferation and differentiation in development, tissue maintenance, wound repair, and angiogenesis. The goal of this review paper is to (i) deliberate on the role of FGFs and FGF receptors (FGFRs) in different cancers, (ii) present advances in FGF-targeted cancer therapies, and (iii) explore cell signaling mechanisms that explain how FGF expression becomes dysregulated during cancer development. FGF is often mutated and overexpressed in cancer and the different FGF and FGFR isoforms have unique expression patterns and distinct roles in different cancers. Among the FGF members, the FGF 15/19 subfamily is particularly interesting because of its unique protein structure and role in endocrine function. The abnormal expression of FGFs in different cancer types (breast, colorectal, hepatobiliary, bronchogenic, and others) is examined and correlated with patient prognosis. The classification of FGF ligands based on their mode of action, whether autocrine, paracrine, endocrine, or intracrine, is illustrated, and an analysis of the binding specificity of FGFs to FGFRs is also provided. Moreover, the latest advances in cancer therapeutic strategies involving small molecules, ligand traps, and monoclonal antibody-based FGF inhibitors are presented. Lastly, we discuss how the dysregulation of FGF and FGFR expression affects FGF signaling and its role in cancer development.

Clinical Significance and Expression Pattern of RIP5 and VGLL4 in Clear Cell Renal Cell Carcinoma Patients Treated with Sunitinib

While clear cell renal cell carcinoma (ccRCC) is curable, advanced metastatic (mRCC) remains a clinical challenge. We analyzed clinical, pathohistological, and molecular data (Receptor Interacting Protein 5-RIP5 and Vestigial Like Family Member 4-VGLL4 expression) of 55 mRCC patients treated with first-line treatment with sunitinib. The trend of linear increase in the protein expression of RIP5 was observed with the progression of tumor grade. Overall, 80% of RIP5-positive cells were in the control kidneys and high-grade mRCC. On the contrary, RIP5 displayed low expression in grade 2 mRCC (5.63%). The trend of linear decrease in the expression of VGLL4 was observed with the progression of tumor grade. The highest protein expression of VGLL4 was observed in grade 2 (87.82%) in comparison to grade 3 and 4 and control. High expression of RIP5 mRNA was associated with longer first-line overall survival and longer progression-free survival in mRCC. In addition, a high VGLL4 mRNA expression showed better overall survival in patients with ccRCC. In conclusion, high mRNA expression of RIP5 and VGLL4 are important markers of better survival rates in mRCC patients.

MSX1-expression during the different phases in healthy human endometrium

PURPOSE

The human endometrium consists of different layers (basalis and functionalis) and undergoes different phases throughout the menstrual cycle. In a former paper, our research group was able to describe MSX1 as a positive prognosticator in endometrial carcinomas. The aim of this study was to examine the MSX1 expression in healthy endometrial tissue throughout the different phases to gain more insight on the mechanics of MSX-regulation in the female reproductive system.

MATERIALS AND METHODS

In this retrospective study, we investigated a total of 17 normal endometrial tissues (six during proliferative phase and five during early and six during late secretory phase). We used immunohistochemical staining and an immunoreactive score (IRS) to evaluate MSX1 expression. We also investigated correlations with other proteins, that have already been examined in our research group using the same patient collective.

RESULTS

MSX1 is expressed in glandular cells during the proliferative phase and downregulated at early and late secretory phase (p = 0.011). Also, a positive correlation between MSX1 and the progesterone-receptor A (PR-A) (correlation coefficient (cc) = 0.0671; p = 0.024), and the progesterone receptor B (PR-B) (cc = 0.0691; p = 0.018) was found. A trend towards negative correlation was recognized between MSX1 and Inhibin Beta-C-expression in glandular cells (cc = - 0.583; p-value = 0.060).

CONCLUSION

MSX1 is known as a member of the muscle segment homeobox gene family. MSX1 is a p53-interacting protein and overexpression of homeobox MSX1 induced apoptosis of cancer cells. Here we show that MSX1 is expressed especially in the proliferative phase of glandular epithelial tissue of the normal endometrium. The found positive correlation between MSX1 and progesterone receptors A and B confirms the results of a previous study on cancer tissue by our research group. Because MSX1 is known to be downregulated by progesterone, the found correlation of MSX1 and both PR-A and -B may represent a direct regulation of the MSX1 gene by a PR-response element. Here further investigation would be of interest.

miR-6742-5p regulates the invasion and migration of lung adenocarcinoma cells via mediating FGF8/ERK12/MMP9/MMP2 signaling pathway

BACKGROUND

microRNAs (miRNAs) are involved in the progression of Lung adenocarcinoma (LUAD), however, the functions of miR-6742-5p in LUAD remains unknown, thereby this study was carried on.

METHODS

The mRNA and miRNA expression data from the LUAD and normal control were obtained from Gene Expression Omnibus (GEO) database, TargetScan and mirDIP were applied to predict the relationship between miR-6742-5p and FGF8.Q-PCR, western blot, dual-luciferase, wound Healing and transwell assays were performed to test the functions of miR-6742-5p in LUAD.

RESULTS

Bioinformatics analysis and dual-luciferase identified FGF8 is the target-gene of miR-6742-5p, which is declined in LUAD of human tissues and cell lines, and miR-6742-5P OE suppressed the progression of LUAD in nude mice. MiR-6742-5p OE and KD suppressed or increased the abilities of LUAD' metastasis tested by wound healing and transwell assays H522 and PC-9 cells, these effects about miR-6742-5p OE were reversed by FGF8; miR-6742-5p OE, KD inhibited and increased the expression of FGF8 as its downstream p-ERK1/2, MMP-2/-9, these results were corrected by ERK1/2 inhibitor: Ro 67-7476; the miR-6742-5p KD increased the migrated and invaded cells and suppressed by MMPs inhibitor: S3304. These results identified the negative correlation of miR-6742-5p with FGF8-ERK1/2 signal pathway in LUAD progression.

CONCLUSIONS

We conclude that miR-6742-5p might be a regulator of LUAD progression by targeting FGF8/ERK1/2/MMPs signaling pathway, which provides a novel therapeutic target for LUAD.

Aberrations in FGFR1, FGFR2, and RIP5 Expression in Human Congenital Anomalies of the Kidney and Urinary Tract (CAKUT)

This study aimed to explore the spatio-temporal expression patterns of congenital anomalies of kidney and urinary tract (CAKUT) candidate genes, Fibroblast Growth Factor Receptor 1 (FGFR1), Fibroblast Growth Factor Receptor 2 (FGFR2) and Receptor-Interacting Protein Kinase 5 (RIP5), in human fetal kidney development (CTRL) and kidneys affected with CAKUT. Human fetal kidneys from the 22nd to 41st developmental week (duplex, hypoplastic, dysplastic, and controls) were stained with antibodies and analyzed by epifluorescence microscopy and RT-qPCR. The effect of CAKUT candidate genes on kidney nephrogenesis and function is confirmed by statistically significant variations in the spatio-temporal expression patterns of the investigated markers. The nuclear localization of FGFR1, elevated expression score of FGFR1 mRNA, the increased area percentage of FGFR1-positive cells in the kidney cortex, and the overall decrease in the expression after the peak at the 27th developmental week in dysplastic kidneys (DYS), suggest an altered expression pattern and protein function in response to CAKUT pathophysiology. The RT-qPCR analysis revealed a significantly higher FGFR2 mRNA expression score in the CAKUT kidneys compared to the CTRL. This increase could be due to the repair mechanism involving the downstream mediator, Extracellular Signal-Regulated Kinase 1/2 (ERK1/2). The expression of RIP5 during normal human kidney development was reduced temporarily, due to urine production and increased later since it undertakes additional functions in the maturation of the postnatal kidney and homeostasis, while the expression dynamics in CAKUT-affected kidneys exhibited a decrease in the percentage of RIP5-positive cells during the investigated developmental period. Our findings highlight the importance of FGFR1, FGFR2, and RIP5 as markers in normal and pathological kidney development.

Immunohistochemical Expression Pattern of FGFR1, FGFR2, RIP5, and HIP2 in Developing and Postnatal Kidneys of Dab1-/- (yotari) Mice

This study aimed to explore how Dab1 gene functional silencing influences the spatial and temporal expression patterns of fibroblast growth factor receptor 1 (FGFR1), fibroblast growth factor receptor 2 (FGFR2), receptor-interacting protein kinase 5 (RIP5), and huntingtin-interacting protein 2 (HIP2) in the developing and postnatal kidneys of the yotari mice as potential determinants of normal kidney formation and function. Dab1^-/- animal kidneys exhibit diminished FGFR1/FGFR2 expression in all examined developmental stages, whereas RIP5 cell immunoreactivity demonstrated negligible variation. The HIP2 expression revealed a discernible difference during the postnatal period, where we noted a significant decrease in almost all the observed kidney structures of yotari animals. An extracellular signal-regulated kinase (Erk1/2) and mammalian target of rapamycin (mTOR) expression in yotari kidneys decreased in embryonic and postnatal developmental phases for which we can hypothesize that the Erk1/2 signaling pathway in the yotari mice kidneys is dependent on Reelin with Dab1 only partially implicated in Reelin-mediated MEK/Erk1/2 activation. The impairment of FGFR1 and FGFR2 expression suggests the involvement of the observed markers in generating the CAKUT phenotype resulting in renal hypoplasia. Our study demonstrates the critical role of HIP2 in reducing cell death throughout nephrogenesis and maturation in wild-type mice and indicates a possible connection between decreased HIP2 expression in postnatal kidney structures and observed podocyte injury in yotari. Our results emphasize the crucial function of the examined markers throughout normal kidney development and their potential participation in kidney pathology and diagnostics, where they might serve as biomarkers and therapeutic targets.

ROR2 downregulation activates the MSX2/NSUN2/p21 regulatory axis and promotes dental pulp stem cell senescence

Cellular senescence severely limits the research and the application of dental pulp stem cells (DPSCs). A previous study conducted by our research group revealed a close implication of ROR2 in DPSC senescence, although the mechanism underlying the regulation of ROR2 in DPSCs remains poorly understood so far. In the present study, it was revealed that the expression of the ROR2-interacting transcription factor MSX2 was increased in aging DPSCs. It was demonstrated that the depletion of MSX2 inhibits the senescence of DPSCs and restores their self-renewal capacity, and the simultaneous overexpression of ROR2 enhanced this effect. Moreover, MSX2 knockdown suppressed the transcription of NSUN2, which regulates the expression of p21 by binding to and causing the m5C methylation of the 3'-UTR of p21 mRNA. Interestingly, ROR2 downregulation elevated the levels of MSX2 protein, and not the MSX2 mRNA expression, by reducing the phosphorylation level of MSX2 and inhibiting the RNF34-mediated MSX2 ubiquitination degradation. The results of the present study demonstrated the vital role of the ROR2/MSX2/NSUN2 axis in the regulation of DPSC senescence, thereby revealing a potential target for antagonizing DPSC aging.

The role of fibroblast growth factor 8 in cartilage development and disease

Fibroblast growth factor 8 (FGF‐8), also known as androgen‐induced growth factor (AIGF), is presumed to be a potent mitogenic cytokine that plays important roles in early embryonic development, brain formation and limb development. In the bone environment, FGF‐8 produced or received by chondrocyte precursor cells binds to fibroblast growth factor receptor (FGFR), causing different levels of activation of downstream signalling pathways, such as phospholipase C gamma (PLCγ)/Ca²⁺, RAS/mitogen‐activated protein kinase‐extracellular regulated protein kinases (RAS/MAPK‐MEK‐ERK), and Wnt‐β‐catenin‐Axin2 signalling, and ultimately controlling chondrocyte proliferation, differentiation, cell survival and migration. However, the molecular mechanism of FGF‐8 in normal or pathological cartilage remains unclear, and thus, FGF‐8 represents a novel exploratory target for studies of chondrocyte development and cartilage disease progression. In this review, studies assessing the relationship between FGF‐8 and chondrocytes that have been published in the past 5 years are systematically summarized to determine the probable mechanism and physiological effect of FGF‐8 on chondrocytes. Based on the existing research results, a therapeutic regimen targeting FGF‐8 is proposed to explore the possibility of treating chondrocyte‐related diseases.

FGF2 and FGF10 expression patterns in the epidermis and mesenchyme during homeotic transformation of tail into hindlimbs in frog tadpoles

Limbs are trunk quintessential in tetrapods. Their development relies on the Retinoic acid (RA) gradient in association with the Fibroblast Growth Factors (FGFs). The role of various FGFs have been probed extensively and confirmed during the induction of ectopic limbs in vertebrates. On such factual backdrops, we studied the expression patterns of FGF2 and FGF10 in the epidermis and mesenchyme by immunohistochemical localization in the regenerating tails of tadpoles of the Indian tree frog, Polypedates maculatus. These tadpoles are known to exhibit a kind of homeotic transformation of tail to limbs during regeneration, whose exact mechanism is still to be established by scientific investigations. Here in this study, we provide the first evidence of the putative involvement of FGF2 and FGF10 during such ectopic appendage development.

The Role of Fibroblast Growth Factor (FGF) Signaling in Tissue Repair and Regeneration

Fibroblast growth factors (FGFs) are a large family of secretory molecules that act through tyrosine kinase receptors known as FGF receptors. They play crucial roles in a wide variety of cellular functions, including cell proliferation, survival, metabolism, morphogenesis, and differentiation, as well as in tissue repair and regeneration. The signaling pathways regulated by FGFs include RAS/mitogen-activated protein kinase (MAPK), phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)–protein kinase B (AKT), phospholipase C gamma (PLCγ), and signal transducer and activator of transcription (STAT). To date, 22 FGFs have been discovered, involved in different functions in the body. Several FGFs directly or indirectly interfere with repair during tissue regeneration, in addition to their critical functions in the maintenance of pluripotency and dedifferentiation of stem cells. In this review, we summarize the roles of FGFs in diverse cellular processes and shed light on the importance of FGF signaling in mechanisms of tissue repair and regeneration.

Expression and localization of FGFR1, FGFR2 and CTGF during normal human lung development

Aim of our study was to provide insight into the temporal and spatial expression of FGFR1, FGFR2 and CTGF during normal human lung development which may have an important impact on understanding occurrence of developmental lung anomalies. Morphological parameters were analysed using double immunofluorescence on human embryonal (6th and 7th developmental week-dw) and foetal (8th, 9th and 16th developmental week) human lung samples. FGFR1 and FGFR2 was positive during all the dw in both the epithelium and mesenchyme. The highest number of FGFR1 positive cells was observed during the 6th dw (112/mm²) and 9th dw (87/mm²) in the epithelium compared to the 7th, 8th and 16th dw (Kruskal-Wallis test, p < 0.001, p < 0.0001). The highest number of FGFR1 positive cells in the mesenchyme was observed during the 8th dw (19/mm²) and 16th dw (13/mm²) compared to the 6th, 7th, and 9th dw (Kruskal-Wallis test, p < 0.001, p < 0.0001). The number of FGFR1 positive cells in the epithelium was higher for FGFR2 compared to number of positive cells (Mann-Whitney test, p < 0.0001). FGFR2 showed the highest number in the epithelium during the 7th dw (111/mm²) and 9th dw (87/mm²) compared to 6th, 8th and 16th dw (Kruskal-Wallis test, p < 0.001, p < 0.0001, p < 0.01 respectively). The highest number of FGFR2 positive cells in the mesenchyme was observed during the 9th dw (26/mm²), compared to the 6th, 7th,8th and 16th dw (Kruskal-Wallis test, p < 0.0001), while the number of FGFR2 positive cells in the epithelium was significantly higher than in the mesenchyme (Mann-Whitney test, p < 0.0001). CTGF was negative in both epithelium and mesenchyme during all except the 16th dw in the mesenchyme where it co-localized with FGFR2. FGFR1 and FGFR2 might be essential for epithelial-mesenchymal interactions that determine epithelial branching and mesenchymal growth during early lung development. Sudden increase in FGF1 in the epithelium and FGF2 in the mesenchyme in the foetus at 9th dw could be associated with the onset of foetal breathing movements. CTGF first appear during the foetal lung development.

MSX1-A Potential Marker for Uterus-Preserving Therapy of Endometrial Carcinomas

Prognostic factors are of great interest in patients with endometrial cancer. One potential factor could be the protein MSX1, a transcription repressor, that has an inhibitory effect on the cell cycle. For this study, endometrioid endometrial carcinomas (n = 53), clear cell endometrial carcinomas (n = 6), endometrioid ovarian carcinomas (n = 19), and clear cell ovarian carcinomas (n = 11) were immunochemically stained for the protein MSX1 and evaluated using the immunoreactive score (IRS). A significant stronger expression of MSX1 was found in endometrioid endometrial carcinomas (p < 0.001), in grading 2 (moderate differentiation) (p = 0.001), and in tumor material of patients with no involvement of lymph nodes (p = 0.031). Correlations were found between MSX1 expression and the expression of β-Catenin, p21, p53, and the steroid receptors ERα, ERβ, PRα, and PRβ. A significant (p = 0.023) better survival for patients with an MSX1 expression in more than 10% of the tumor cells was observed for endometrioid endometrial carcinomas (21.3 years median survival (MSX1-positive) versus 17.3 years (MSX1-negative)). Although there is evidence that MSX1 expression correlates with improved long-term survival, further studies are necessary to evaluate if MSX1 can be used as a prognostic marker.

Spatio-temporal patterning of different connexins in developing and postnatal human kidneys and in nephrotic syndrome of the Finnish type (CNF)

Connexins (Cxs) are membrane-spanning proteins which enable flow of information important for kidney homeostasis. Changes in their spatiotemporal patterning characterize blood vessel abnormalities and chronic kidney diseases (CKD). We analysed spatiotemporal expression of Cx37, Cx40, Cx43 and Cx45 in nephron and glomerular cells of developing, postnatal kidneys, and nephrotic syndrome of the Finnish type (CNF) by using immunohistochemistry, statistical methods and electron microscopy. During kidney development, strong Cx45 expression in proximal tubules and decreasing expression in glomeruli was observed. In developing distal nephron, Cx37 and Cx40 showed moderate-to-strong expression, while weak Cx43 expression gradually increased. Cx45/Cx40 co-localized in mesangial and granular cells. Cx43 /Cx45 co-localized in podocytes, mesangial and parietal epithelial cells, and with podocyte markers (synaptopodin, nephrin). Different Cxs co-expressed with endothelial (CD31) and VSMC (α -SMA) markers in vascular walls. Peak signalling of Cx37, Cx43 and Cx40 accompanied kidney nephrogenesis, while strongest Cx45 signalling paralleled nephron maturation. Spatiotemporal Cxs patterning indicate participation of Cx45 in differentiation of proximal tubules, and Cx43, Cx37 and Cx40 in distal tubules differentiation. CNF characterized disorganized Cx45 expression in proximal tubules, increased Cx43 expression in distal tubules and overall elevation of Cx40 and Cx37, while Cx40 co-localized with increased number of interstitial myofibroblasts.

MSX2 suppression through inhibition of TGFβ signaling enhances hematopoietic differentiation of human embryonic stem cells

Background

Strategies of generating functional blood cells from human pluripotent stem cells (hPSCs) remain largely unsuccessful due to the lack of a comprehensive understanding of hematopoietic development. Endothelial-to-hematopoietic transition (EHT) serves as the pivotal mechanism for the onset of hematopoiesis and is negatively regulated by TGF-β signaling. However, little is known about the underlying details of TGF-β signaling during EHT.

Methods

In this study, by applying genome-wide gene profiling, we identified muscle segment homeobox2 (MSX2) as a potential mediator of TGF-β signaling during EHT. We generated MSX2-deleted human embryonic stem cell (hESC) lines using the CRISPR/Cas9 technology and induced them to undergo hematopoietic differentiation. The role of MSX2 in hematopoiesis and functional regulation of TGFβ signaling in EHT was studied.

Results

We identified MSX2 as a novel regulator of human hematopoiesis. MSX2 deletion promotes the production of hematopoietic cells from hESCs. Functional and bioinformatics studies further demonstrated that MSX2 deletion augments hematopoietic differentiation of hESCs by facilitating EHT. Mechanistically, MSX2 acts as a downstream target of TGFβ signaling to mediate its function during EHT.

Conclusions

Our results not only improve the understanding of EHT, but may also provide novel insight into the efficient production of functional blood cells from hPSCs for regenerative medicine.

Evaluation of dynamic developmental processes and the molecular basis of the high body fat percentage of different proglottid types of Moniezia expansa

BACKGROUND

Moniezia expansa (Cyclophyllidea: Anoplocephalidae) is a large species of tapeworm that occurs in sheep and cattle and inhabits the small intestine, causing diarrhea and weight declines, leading to stockbreeding losses. Interestingly, the body fat percentage of M. expansa, which lacks the ability to synthesize fatty acids, is as high as 78% (dry weight) and all of the proglottids of M. expansa exhibit a dynamic developmental process from top to bottom. The aim of this paper is to identify the molecular basis of this high body fat percentage, the dynamic expression of developmental genes and their expression regulation patterns.

RESULTS

From 12 different proglottids (four sections: scolex and neck, immature, mature and gravid with three replicates), 13,874 transcripts and 680 differentially expressed genes (DEGs) were obtained. The gene expression patterns of the scolex and neck and immature proglottids were very similar, while those of the mature and gravid proglottids differed greatly. In addition, 13 lipid transport-related proteins were found in the DEGs, and the expression levels showed an increasing trend in the four proglottid types. Furthermore, it was shown that 33 homeobox genes, 9 of which were DEGs, had the highest expression in the scolex and neck section. The functional enrichment results of the DEGs were predominantly indicative of development-related processes, and there were also some signal transduction and metabolism results. The most striking result was the finding of Wnt signaling pathways, which appeared multiple times. Furthermore, the weighted gene co-expression networks were divided into 12 modules, of which the brown module was enriched with many development-related genes.

CONCLUSIONS

We hypothesize that M. expansa uses lipid transport-associated proteins to transport lipids from the host gut to obtain energy to facilitate its high fecundity. In addition, homeobox genes and Wnt signaling pathways play a core role in development and regeneration. The results promote research on the cell differentiation involved in the continuous growth and extension of body structures.

Comprehensive clinical and molecular studies in split-hand/foot malformation: identification of two plausible candidate genes (LRP6 and UBA2)

Split-hand/foot malformation (SHFM) is a clinically and genetically heterogeneous condition. We sequentially performed screening of the previously identified Japanese founder 17p13.3 duplication/triplication involving BHLHA9, array comparative genomic hybridization, and whole exome sequencing (WES) in newly recruited 41 Japanese families with non-syndromic and syndromic SHFM. We also carried out WES in seven families with nonsyndromic and syndromic SHFM in which underlying genetic causes including pathogenic copy-number variants (CNVs) remained undetected in our previous studies of 56 families. Consequently, we identified not only known pathogenic CNVs (17p13.3 duplications/triplications [n = 21], 2q31 deletion [n = 1], and 10q24 duplications [n = 3]) and rare variants in known causative genes (TP63 [n = 3], DLX5 [n = 1], IGF2 [n = 1], WNT10B [n = 3], WNT10B/PORCN [n = 1], and PORCN [n = 1]), but also a de novo 19q13.11 deletion disrupting UBA2 (n = 1) and variants that probably affect function in LRP6 (n = 1) and UBA2 (n = 1). Thus, together with our previous data based on testing of 56 families, molecular studies for a total of 97 families with SHFM revealed underlying genetic causes in 75 families, and clinical studies for the 75 families indicated a certain degree of correlation between genetic causes and phenotypes. The results imply that SHFM primarily occurs as a genetic disorder with genotype-phenotype correlations. Furthermore, the results together with previous data such as the development of SHFM in Lrp6 knockout mice, the presence of SHFM in two subjects with 19q13 deletions involving UBA2, and strong mouse Uba2 expression in the developing limb buds, imply that LRP6 and UBA2 represent plausible candidate genes for SHFM.

Immunohistochemical expression pattern of RIP5, FGFR1, FGFR2 and HIP2 in the normal human kidney development

AIM

Present study analyses the co-localisation of RIP5 with FGFR1, FGFR2 and HIP2 in the developing kidney, as RIP5 is a major determinant of urinary tract development, downstream of FGF-signaling.

METHODS

Paraffin embedded human kidney tissues of 16 conceptuses between the 6th-22th developmental week were analysed using double-immunofluorescence method with RIP5/FGFR1/FGFR2 and HIP2 markers. Quantification of positive cells were performed using Kruskal-Wallis test.

RESULTS

In the 6th week of kidney development RIP5 (89.6%) and HIP2 (39.6%) are strongly expressed in the metanephric mesenchyme. FGFR1 shows moderate/strong expression in the developing nephrons (87.3%) and collecting ducts (70.5%) (p < 0.05). RIP5/FGFR1 co-localized at the marginal zone and the ureteric bud with predominant FGFR1 expression. FGFR2 (26.1%) shows similar expression pattern as FGFR1 (70.5%) in the same kidney structures. RIP5/FGFR2 co-localized at the marginal zone and the collecting ducts (predominant expression of FGFR2). HIP2 is strongly expressed in collecting ducts (96.7%), and co-localized with RIP5. In 10th week, RIP5 expression decrease (74.2%), while the pattern of expression of RIP5 and FGFR1 in collecting ducts (33.4% and 91.9%) and developing nephrons (21.9% and 32.4%) (p < 0.05) is similar to that in the 6th developmental week. Ureter is moderately expressing RIP5 while FGFR1 is strongly expressed in the ureteric wall. FGFR2 is strongly expressed in the collecting ducts (84.3%) and ureter. HIP2 have 81.1% positive cells in the collecting duct. RIP5/FGFR1 co-localize in collecting ducts and Henley's loop.

CONCLUSIONS

The expression pattern of RIP5, FGFR1, FGFR2 and HIP2 in the human kidney development might indicate their important roles in metanephric development and ureteric muscle layer differentiation through FGF signaling pathways.

LHX2 Mediates the FGF-to-SHH Regulatory Loop during Limb Development

During limb development, fibroblast growth factors (Fgfs) govern proximal⁻distal outgrowth and patterning. FGFs also synchronize developmental patterning between the proximal⁻distal and anterior⁻posterior axes by maintaining Sonic hedgehog (Shh) expression in cells of the zone of polarizing activity (ZPA) in the distal posterior mesoderm. Shh, in turn, maintains Fgfs in the apical ectodermal ridge (AER) that caps the distal tip of the limb bud. Crosstalk between Fgf and Shh signaling is critical for patterned limb development, but the mechanisms underlying this feedback loop are not well-characterized. Implantation of Fgf beads in the proximal posterior limb bud can maintain SHH expression in the former ZPA domain (evident 3 h after application), while prolonged exposure (24 h) can induce SHH outside of this domain. Although temporally and spatially disparate, comparative analysis of transcriptome data from these different populations accentuated genes involved in SHH regulation. Comparative analysis identified 25 candidates common to both treatments, with eight linked to SHH expression or function. Furthermore, we demonstrated that LHX2, a LIM Homeodomain transcription factor, is an intermediate in the FGF-mediated regulation of SHH. Our data suggest that LHX2 acts as a competency factor maintaining distal posterior SHH expression subjacent to the AER.