Functional missense and splicing variants in the retinoic acid catabolizing enzyme CYP26C1 in idiopathic short stature

Toxic effects and toxicological mechanisms of chlorinated paraffins: A review for insight into species sensitivity and toxicity difference

Chlorinated paraffins (CPs), a group of chlorinated alkane mixtures, are frequently detected in various environmental matrices and human bodies. Recently, CPs have garnered considerable attention owing to their potential to induce health hazards in wildlife and human. Several reviews have discussed short-chain CPs (SCCPs) induced ecological risk; however, a comprehensive understanding of the underlying toxic mechanisms and a comparison among SCCPs, medium-, and long-chain CPs (MCCPs and LCCPs, respectively) are yet to be established. This review summarizes the latest research progress on the toxic effects and the underlying molecular mechanisms of CPs. The main toxicity mechanisms of CPs include activation of several receptors, oxidative stress, disturbance of energy metabolism, and inhibition of gap junction-mediated communication. The sensitivity of different species to CP-mediated toxicities varies markedly, with aquatic organisms exhibiting the highest sensitivity to CP-induced toxicity. The toxicity comparison analysis indicated that MCCPs may be unsafe as potential substitutes for SCCPs.

Leri-Weill Dyschondrosteosis Caused by a Leaky Homozygous SHOX Splice-Site Variant

SHOX deficiency is a common genetic cause of short stature of variable degree. SHOX haploinsufficiency causes Leri-Weill dyschondrosteosis (LWD) as well as nonspecific short stature. SHOX haploinsufficiency is known to result from heterozygous loss-of-function variants with pseudo-autosomal dominant inheritance, while biallelic SHOX loss-of-function variants cause the more severe skeletal dysplasia, Langer mesomelic dyschondrosteosis (LMD). Here we report for the first time the pseudo-autosomal recessive inheritance of LWD in two siblings caused by a novel homozygous non-canonical, leaky splice-site variant in intron 3 of SHOX: c.544+5G>C. Transcript analyses in patient-derived fibroblasts showed homozygous patients to produce approximately equal amounts of normally spliced mRNA and mRNA with the abnormal retention of intron 3 and containing a premature stop codon (p.Val183Glyfs*31). The aberrant transcript was shown to undergo nonsense-mediated mRNA decay, and thus resulting in SHOX haploinsufficiency in the homozygous patient. Six healthy relatives who are of normal height are heterozygous for this variant and fibroblasts from a heterozygote for the c.544+5G>C variant produced wild-type transcript amounts comparable to healthy control. The unique situation reported here highlights the fact that the dosage of SHOX determines the clinical phenotype rather than the Mendelian inheritance pattern of SHOX variants. This study extends the molecular and inheritance spectrum of SHOX deficiency disorder and highlights the importance of functional testing of SHOX variants of unknown significance in order to allow appropriate counseling and precision medicine for each family individual.

LCN2 is a new diagnostic biomarker and potential therapeutic target in idiopathic short stature

Idiopathic short stature (ISS) is the most common paediatric endocrine disease. However, the underlying pathology of ISS remains unclear. Currently, there are no effective diagnostic markers or therapeutic strategies available for ISS. In this study, we aimed to identify differential plasma protein expression and novel biomarkers in patients with ISS, and elucidate the biological functions of candidate proteins in ISS pathogenesis. Four specimen pairs from four ISS children and age‐/sex‐matched control individuals were subjected to proteomics analysis, and 340 samples of children with a mean age 9.73 ± 0.24 years were utilized to further verify the differentially expressed proteins by enzyme‐linked immunosorbent assay (ELISA). The receiver‐operating characteristic (ROC) curve and the area under the ROC curve (AUC) were plotted. A total of 2040 proteins were identified, of which 84 were differentially expressed. In vitro and in vivo experiments confirmed the biological functions of these candidate proteins. LCN2 overexpression in ISS was verified using ELISA. Meanwhile, LCN2 showed high sensitivity and specificity in discriminating children with ISS from those with growth hormone deficiency, precocious puberty and normal control individuals. The upregulated expression of LCN2 not only suppressed food intake but also impaired chondrocyte proliferation and bone growth in chondrocytes and rats. As a result, the rats presented a short‐stature phenotype. Subsequently, we found that bone growth inhibition recovered after LCN2 overexpression was stopped in immature rats. To our knowledge, this is the first study to report that LCN2 may be a significant target for ISS diagnosis and treatment.

Identification and Tissue-Specific Characterization of Novel SHOX-Regulated Genes in Zebrafish Highlights SOX Family Members Among Other Genes

SHOX deficiency causes a spectrum of clinical phenotypes related to skeletal dysplasia and short stature, including Léri-Weill dyschondrosteosis, Langer mesomelic dysplasia, Turner syndrome, and idiopathic short stature. SHOX controls chondrocyte proliferation and differentiation, bone maturation, and cellular growth arrest and apoptosis via transcriptional regulation of its direct target genes NPPB, FGFR3, and CTGF. However, our understanding of SHOX-related pathways is still incomplete. To elucidate the underlying molecular mechanisms and to better understand the broad phenotypic spectrum of SHOX deficiency, we aimed to identify novel SHOX targets. We analyzed differentially expressed genes in SHOX-overexpressing human fibroblasts (NHDF), and confirmed the known SHOX target genes NPPB and FGFR among the most strongly regulated genes, together with 143 novel candidates. Altogether, 23 genes were selected for further validation, first by whole-body characterization in developing shox-deficient zebrafish embryos, followed by tissue-specific expression analysis in three shox-expressing zebrafish tissues: head (including brain, pharyngeal arches, eye, and olfactory epithelium), heart, and pectoral fins. Most genes were physiologically relevant in the pectoral fins, while only few genes were also significantly regulated in head and heart tissue. Interestingly, multiple sox family members (sox5, sox6, sox8, and sox18) were significantly dysregulated in shox-deficient pectoral fins together with other genes (nppa, nppc, cdkn1a, cdkn1ca, cyp26b1, and cy26c1), highlighting an important role for these genes in shox-related growth disorders. Network-based analysis integrating data from the Ingenuity pathways revealed that most of these genes act in a common network. Our results provide novel insights into the genetic pathways and molecular events leading to the clinical manifestation of SHOX deficiency.

New gene discoveries in skeletal diseases with short stature

In the last decade, the widespread use of massively parallel sequencing has considerably boosted the number of novel gene discoveries in monogenic skeletal diseases with short stature. Defects in genes playing a role in the maintenance and function of the growth plate, the site of longitudinal bone growth, are a well-known cause of skeletal diseases with short stature. However, several genes involved in extracellular matrix composition or maintenance as well as genes partaking in various biological processes have also been characterized. This review aims to describe the latest genetic findings in spondyloepiphyseal dysplasias, spondyloepimetaphyseal dysplasias, and some monogenic forms of isolated short stature. Some examples of novel genetic mechanisms leading to skeletal conditions with short stature will be described. Strategies on how to successfully characterize novel skeletal phenotypes with short stature and genetic approaches to detect and validate novel gene-disease correlations will be discussed in detail. In summary, we review the latest gene discoveries underlying skeletal diseases with short stature and emphasize the importance of characterizing novel molecular mechanisms for genetic counseling, for an optimal management of the disease, and for therapeutic innovations.

A Novel Diagnostic Predictive Model for Idiopathic Short Stature in Children

OBJECTIVE

Idiopathic short stature (ISS), an endocrine-related disease, is difficult to diagnose. Previous studies have shown that many children with some inflammation-related diseases often have short stature, but whether inflammation is the underlying mechanism of ISS has not been studied. Here, we attempt to explore the role of inflammation in the occurrence and development of ISS and to demonstrate an available clinical diagnostic model of ISS.

METHODS

Frozen serum samples were collected from ISS patients (n = 4) and control individuals (n = 4). Isobaric tags for relative and absolute quantitation (iTRAQ) combined with LC-MS/MS analysis were applied to quantitative proteomics analysis. To assess clusters of potentially interacting proteins, functional enrichment (GO and KEGG) and protein-protein interaction network analyses were performed, and the crucial proteins were detected by Molecular Complex Detection (MCODE). Furthermore, serum levels of two selected proteins were measured by ELISA between ISS patients (n = 80) and controls (n = 80). In addition, experiments in vitro were used to further explore the effects of crucial proteins on endochondral ossification.

RESULTS

A total of 437 proteins were quantified, and 84 DEPs (60 upregulated and 24 downregulated) were identified between patients with ISS and controls. Functional enrichment analysis showed that the DEPs were primarily enriched in blood microparticle, acute inflammatory response, protein activation cascade, collagen-containing extracellular matrix, platelet degranulation, etc. According to the results of top 10 fold change DEPs and MCODE analysis, C1QA and C1QB were selected to further experiment. The expression levels of C1QA and C1QB were validated in serum samples. Based on the logistic regression analysis and ROC curve analysis, we constructed a novel diagnostic model by serum levels of C1QA and C1QB with a specificity of 91.2% and a sensitivity of 75% (AUC = 0.900, p <0.001). Finally, the western blotting analysis confirmed the expression levels of OCN, OPN, RUNX2, and Collagen X were downregulated in chondrocytes, and the outcome of Collagen II was upregulated.

CONCLUSION

Our study is the first to demonstrate the significant role of inflammation in the development of ISS. In addition, we identify C1QA and C1QB as novel serum biomarkers for the diagnosis of ISS.

Hsa_circularRNA_0079201 suppresses chondrocyte proliferation and endochondral ossification by regulating the microRNA‑140‑3p/SMAD2 signaling pathway in idiopathic short stature

Circular (circ)RNAs are an important group of non-coding RNAs involved in different pathological and physiological functions, such as longitudinal bone growth. However, the effects of an increase or decrease in circRNA expression on idiopathic short stature (ISS) remain largely unknown. The present study compared the circRNA expression patterns of patients with ISS and healthy individuals to identify differentially expressed circRNAs involved in the regulation of ISS pathogenesis and their target microRNAs (miR). Microarray analysis revealed that 145 circRNAs were differentially expressed in patients with ISS, including 83 up- and 62 downregulated circRNAs. Reverse transcription-quantitative PCR confirmed that hsa_circRNA_0079201 was increased in patients with ISS compared with that in the normal individuals, whilst hsa_circRNA_0079201 overexpression in human chondrocytes was shown to significantly suppress their proliferation, hypertrophy and endochondral ossification abilities. Luciferase reporter assays identified that circRNA_0079201 acted as an miR-140-3p sponge. In situ hybridization confirmed the co-localization of circRNA_0079201 and miR-140-3p in the human chondrocyte and neonatal femur growth plate of C57 mice, while rescue experiments demonstrated that miR-140-3p overexpression reversed the inhibition of human chondrocyte proliferation, hypertrophy and endochondral ossification, caused by circRNA_0079201 overexpression. Bioinformatics analysis and luciferase reporter assays revealed that SMAD2 was a potential target gene of miR-140-3p. Furthermore, overexpressing circRNA_0079201 in human chondrocytes suppressed miR-140-3p and increased SMAD2 protein expression level. Taken together, chondrocyte proliferation, hypertrophy and endochondral ossification in ISS was suppressed by a novel regulatory axis consisting of the hsa_circRNA_0079201/miR-140-3p/SMAD2 pathway. The present study provided evidence that hsa_circRNA_0079201 may be a potential target for ISS therapy.

Regulating Retinoic Acid Availability during Development and Regeneration: The Role of the CYP26 Enzymes

This review focuses on the role of the Cytochrome p450 subfamily 26 (CYP26) retinoic acid (RA) degrading enzymes during development and regeneration. Cyp26 enzymes, along with retinoic acid synthesising enzymes, are absolutely required for RA homeostasis in these processes by regulating availability of RA for receptor binding and signalling. Cyp26 enzymes are necessary to generate RA gradients and to protect specific tissues from RA signalling. Disruption of RA homeostasis leads to a wide variety of embryonic defects affecting many tissues. Here, the function of CYP26 enzymes is discussed in the context of the RA signalling pathway, enzymatic structure and biochemistry, human genetic disease, and function in development and regeneration as elucidated from animal model studies.

Early Life Stage Bioactivity Assessment of Short-Chain Chlorinated Paraffins at Environmentally Relevant Concentrations by Concentration-Dependent Transcriptomic Analysis of Zebrafish Embryos

Short-chain chlorinated paraffins (SCCPs), a class of ubiquitous pollutants, are considered to be embryotoxic and teratogenic. However, little is known regarding the bioactivity and mechanisms at environmentally relevant concentrations at the embryonic period. Here, a concentration-dependent reduced transcriptomic approach was used to evaluate the environmental dose (<100 ppb) effects of nine SCCP congeners and eight commercial mixtures on zebrafish embryos at 8 hpf. After 24 h of exposure, the overall biological potency of all the SCCPs, in terms of interference with 20% of the differentially expressed genes (POD_DEG20), in zebrafish embryos ranged from 0.83 to 67.61 ppb. C₁₀H₁₄Cl₈ (POD_GO20 = 3.80 ppb) and C_10-13 51.5% Cl (POD_GO20 = 3.31 ppb) exhibited the strongest interference with biological processes compared to other SCCP homologs and mixtures, respectively. The most sensitive early molecular responses induced by SCCPs were associated with pathways of genetic damage, energy metabolite interference, and metal ion binding. Furthermore, the carbon number was positively correlated with the transcriptomic potency (POD_GO20) of SCCP congeners (with chlorine content > 60%) (p = 0.038), and the chlorine content of SCCP congeners affected the bioactivity associated with genotoxic pathways. The concentration-dependent reduced transcriptomic approach significantly improved the understanding of the ecological risk of environmental contaminants at early life stages.

Achieving Optimal Short- and Long-term Responses to Paediatric Growth Hormone Therapy

It is over sixty years since the first administration of human growth hormone (GH) to children with GH deficiency, and over thirty years since recombinant human GH has been available for treatment of GH deficiency and a wider range of non-GH deficiency disorders. From a diagnostic perspective, genetic analysis, using single gene or Sanger sequencing and more recently next generation or whole exome sequencing, has brought advances in the diagnosis of specific causes of short stature, which has enabled therapy to be targeted more accurately. Genetic discoveries have ranged from defects of pituitary development and GH action to abnormalities in intracellular mechanisms, paracrine regulation and cartilage matrix formation. The strategy of GH therapy using standard doses has evolved to individualised GH dosing, depending on diagnosis and predictors of growth response. Evidence of efficacy of GH in GH deficiency, Turner syndrome and short children born small for gestational age is reviewed. The importance of critical assessment of growth response is discussed, together with the recognition and management of a poor or unsatisfactory growth response and the organisational issues related to prevention, detection and intervention regarding suboptimal adherence to GH therapy.