High frequency of pathogenic ACAN variants including an intragenic deletion in selected individuals with short stature

A rare ACAN non-canonical splicing-site intron variant results in familial short stature

OBJECTIVE

ACAN gene variants, prevalent monogenic defects linked to short stature, are characterized by impaired cartilage generation in growth plates. We aimed to unravel the genetic basis of short stature in a specific pedigree by investigating the role of a novel non-canonical splicing-site variant, c.630-13G > A, within the ACAN gene.

METHOD

Sanger sequencing was used for pedigree verification, and the effects of this variant on mRNA splicing were analyzed through minigene assay.

RESULTS

The study revealed that this variant led to the creation of a previously unreported splice site in the fourth intron, resulting in the incorporation of an 11 bp sequence from the intron into the final transcript. This alteration led to a frameshift and formation of a premature termination codon, impacting the structure of the aggrecan protein.

CONCLUSIONS

We document the pathogenicity of an ACAN non-canonical splicing-site variant, emphasizing the significance of considering intronic variants during genetic testing.

A rare case of skeletal dysplasia: biallelic variant in ACAN gene

OBJECTIVES

Spondylo-epimetaphyseal dysplasia-aggregan (SEMD-ACAN) is a rare form of osteo-chondrodysplasia that includes vertebral, epiphyseal and metaphyseal dysplasia. It occurs as a result of loss-of-function mutations in the ACAN gene, which encodes aggregan protein, which is the basic component of the extracellular matrix in cartilage. It results in disproportionately short stature and skeletal abnormalities. Here, we aimed to present the fourth SEMD-ACAN report in the literature.

CASE PRESENTATION

A 9-year-old girl was admitted to our clinic with growth retardation. She was born from a first-degree cousin marriage with severe short stature (41 cm; -3.54 SDS). Her mother also had severe short stature. Her height was 110 cm (-4.6 SDS); she had midface hypoplasia, low-set ears, short neck, short limbs, and central obesity. Biochemical and hormonal tests were normal. Skeletal survey showed moderate platyspondylia, thoracolumbar scoliosis, lumbar lordosis, bilateral femoro-acetabular narrowing, and advanced bone age (10 years). The patient's brother was 100 cm (-3.97 SDS). He had similar but milder clinical findings. Biallelic ACAN variation (c.512C>T; p. Ala171Val) was detected in two siblings by next-generation sequencing. The parents were heterozygous carriers. Before, the heterozygous form of this variant has been reported in a 15-year-old boy with short stature, advanced bone age, and dysmorphic features.

CONCLUSIONS

SEMD-ACAN is a rare genetic condition that affects bone growth and development and can cause physical and developmental abnormalities. This article highlights the importance of considering genetic testing in characteristic symptoms associated with SEMD-ACAN, such as severe growth retardation and skeletal abnormalities.

A Case of Short Stature Caused by a Mutation in the ACAN Gene

Introduction

Aggrecanopathies are rare disorders associated with idiopathic short stature. They are caused by pathogenic changes in the ACAN gene located on chromosome 15q26. In this study, we present a case of short stature caused by mutations in the ACAN gene.

Case Presentation

A 3-year-3-month-old male patient was referred to us because of his short stature. Physical examination revealed proportional short stature, frontal bossing, macrocephaly, midface hypoplasia, ptosis in the right eye, and wide toes. When the patient was 6 years and 3 months old, his bone age was compatible with 7 years of age. The patient underwent clinical exome sequencing and a heterozygous nonsense c.1243G>T, p.(Glu415*) pathogenic variant was detected in the ACAN gene. The same variant was found in his phenotypically similar father. Our patient is the second case with ptosis.

Discussion

ACAN gene mutation should be considered in the differential diagnosis of patients with idiopathic short stature. The development and widespread use of next-generation sequencing technology has increased the diagnostic and treatment possibilities.

Case report: A novel heterozygous frameshift mutation of ACAN in a Chinese family with short stature and advanced bone age

Short stature (OMIM: 165800) is a common pediatric disorder. Any abnormality in the cartilage formation of the growth plate can cause short stature. Aggrecan, encoded by ACAN, is an important component of the extracellular matrix. Mutations in ACAN have been reported to cause short stature. In the present study, we enrolled a Chinese family with short stature and advanced bone age across three generations. Whole-exome sequencing (WES) was performed on the proband to detect the candidate genes causing short stature in family. A novel heterozygous frameshift mutation (NM_013227.3:c.7230delT; NP_001356197.1: p. Phe2410Leufs*9) of the ACAN gene was confirmed to be a genetic lesion in this family. This variant, which was located in a functional site globular 3 (G3) domain of ACAN and predicted to be deleterious by informatics programs, was co-segregated with the affected family members by performing Sanger sequencing. Literatures review of growth hormone (GH) treatment outcome of all previously reported ACAN patients suggesting that the G3 domain of ACAN may be critical in the development of short stature and growth hormone treatment. These findings not only contribute to the genetic diagnosis and counseling of the family, but will also expand the mutation spectrum of ACAN.

A Novel Heterozygous ACAN Variant in a Short Patient Born Small for Gestational Age with Recurrent Patellar Dislocation: A Case Report

ACAN variants can manifest as various clinical features, including short stature, advanced bone age (BA), and skeletal defects. Here, we report rare clinical manifestations of ACAN defects in a 9 year, 5 month-old girl born small for gestational age (SGA), who presented with short stature, and was initially diagnosed with idiopathic growth hormone deficiency. She displayed several dysmorphic features, including genu valgum, cubitus valgus, and recurrent patellar dislocations. She presented with progressive advancement of BA compared with chronological age. Whole exome sequencing confirmed the presence of a novel heterozygous nonsense variant, c.1968C>G, p.(Tyr656*), in ACAN. ACAN variants should be considered in short stature patients born SGA with joint problems, particularly those with recurrent patellar dislocation and genu valgum.

Exploring and expanding the phenotype and genotype diversity in seven Chinese families with spondylo-epi-metaphyseal dysplasia

Spondylo-epi-metaphyseal dysplasia (SEMD) is a heterogeneous group of disorders with different modes of inheritance and is characterized by disproportionate or proportionate short stature. To date, more than 30 disease-causing genes have been identified, and different types of SEMD exhibit greatly overlapping clinical features, which usually complicate the diagnosis. This study was performed to expand the clinical and molecular spectrum of SEMD among Chinese subjects and to explore their potential phenotype–genotype relations. We enrolled seven families including 11 affected patients with SEMD, and their clinical, radiographic, and genetic data were carefully analyzed. All the seven probands showed different degrees of short stature, and each of them exhibited additional specific skeletal manifestations; four probands had extraosseous manifestations. X-rays of the seven probands showed common features of SEMD, including vertebral deformities, irregular shape of the epiphysis, and disorganization of the metaphysis. Seven variants were identified in TRPV4 (c.694C> T, p.Arg232Cys), COL2A1 (c.654 + 1G > C; c.3266_3268del, p.Gly1089del), CCN6 (c.396 T> G, p.Cys132Trp; c.721 T>C, p.Cys241Arg), SBDS (c.258 + 2T> C), and ACAN (c.1508C> A, p.Thr503Lys) genes, and two of them were novel. Two families with TRPV4 variants showed considerable intrafamily and interfamily heterogeneities. In addition, we reported one case of SEMD with a severe phenotype caused by ACAN gene mutation. Our study expands the phenotype and genetic spectrum of SEMD and provides evidence for the phenotype–genotype relations, aiding future molecular and clinical diagnosis as well as procreative management of SEMD.

The Spectrum of ACAN Gene Mutations in a Selected Chinese Cohort of Short Stature: Genotype-Phenotype Correlation

Objective: Mutations in the ACAN gene have been reported to cause short stature. However, the prevalence estimates of pathogenic ACAN variants in individuals with short stature vary, and the correlation between ACAN genotype and clinical phenotype remain to be evaluated. To determine the prevalence of ACAN variants among Chinese people with short stature and analyze the relationship between genotype and main clinical manifestations of short stature and advanced bone age among patients with ACAN variants.

Methods: We performed next-generation sequencing-based genetic analyses on 442 individuals with short stature. ACAN variants were summarized, previously reported cases were retrospectively analyzed, and an association analysis between genotype and phenotype was conducted.

Result: We identified 15 novel and two recurrent ACAN gene variants in 16 different pedigrees that included index patients with short stature. Among the patients with ACAN variants, 12 of 18 had advanced bone age and 7 of 18 received growth hormone therapy, 5 (71.4%) of whom exhibited variable levels of height standard deviation score improvement. Further analysis showed that patients with ACAN truncating variants had shorter height standard deviation scores (p = 0.0001) and larger bone age–chronological age values (p = 0.0464). Moreover, patients in this Asian population had a smaller mean bone age–chronological age value than those that have been determined in European and American populations (p = 0.0033).

Conclusion: Our data suggest that ACAN mutation is a common cause of short stature in China, especially among patients with a family history of short stature but also among those who were born short for their gestational age without a family history. Patients with truncating variants were shorter in height and had more obvious advanced bone age, and the proportion of patients with advanced bone age was lower in this Asian population than in Europe and America.

Identification of variants in ACAN and PAPSS2 leading to spondyloepi(meta)physeal dysplasias in four Chinese families

Background

Spondyloepi(meta)physeal dysplasias (SE[M]D) are a group of inherited skeletal disorders that mainly affect bone and cartilage, and next‐generation sequencing has aided the detection of genetic defects of such diseases. In this study, we aimed to identify causative variants in four Chinese families associated with SE(M)D.

Methods

We recruited four unrelated Chinese families all displaying short stature and growth retardation. Clinical manifestations and X‐ray imaging were recorded for all patients. Candidate variants were identified by whole‐exome sequencing (WES) and verified by Sanger sequencing. Pathogenicity was assessed by conservation analysis, 3D protein modeling and in silico prediction, and was confirmed according to American College of Medical Genetics and Genomics.

Results

Three novel SE(M)D‐related variants c.1090dupG, c.7168 T > G, and c.2947G > C in ACAN, and one reported variant c.712C > T in PAPSS2 were identified. Among them, c.1090dupG in ACAN and c.712C > T in PAPSS2 caused truncated protein and the other two variants led to amino acid alterations. Conservation analysis revealed sites of the two missense variants were highly conserved, and bioinformatic findings confirmed their pathogenicity. 3D modeling of mutant protein encoded by c.7168 T > G(p.Trp2390Gly) in ACAN proved the structural alteration in protein level.

Conclusion

Our data suggested ACAN is a common pathogenic gene of SE(M)D. This study enriched the genetic background of skeletal dysplasias, and expanded the mutation spectra of ACAN and PAPSS2.

Short stature associated with a novel mutation in the aggrecan gene: A case report and literature review

BACKGROUND

Mutations in the aggrecan (ACAN) gene are identified in patients with: spondyloepiphyseal dysplasia, Kimberley type; short stature with advanced bone age (BA); in the presence or absence of heterozygous ACAN mutation-induced early-onset osteoarthritis and/or osteochondritis dissecans; and spondyloepimetaphyseal dysplasia, ACAN type. Heterozygous mutations contribute to spondyloepiphyseal dysplasia, Kimberley type (MIM#608361), which is a milder skeletal dysplasia. In contrast, homozygous mutations cause a critical skeletal dysplasia, which is called spondyloepimetaphyseal dysplasia, ACAN type (MIM#612813). Lately, investigations on exome and genome sequencing have shown that ACAN mutations can also lead to idiopathic short stature with or without an advanced BA, in the presence or absence of early-onset osteoarthritis and/or osteochondritis dissecans (MIM#165800). We herein reported a heterozygous defect of ACAN in a family with autosomal dominant short stature, BA acceleration, and premature growth cessation.

CASE SUMMARY

A 2-year-old male patient visited us due to growth retardation. The patient presented symmetrical short stature (height 79 cm, < -2 SD) without facial features and other congenital abnormalities. Whole-exome sequencing revealed a heterozygous pathogenic variant c. 871C>T (p. Gln291*) of ACAN, which was not yet reported in cases of short stature. This mutation was also detected in his father and paternal grandmother. According to the Human Gene Mutation Database, 67 ACAN mutations are registered. Most of these mutations are genetically inheritable, and very few children with short stature are associated with ACAN mutations. To date, heterozygous ACAN mutations have been reported in approximately 40 families worldwide, including a few individuals with a decelerated BA.

CONCLUSION

Heterozygous c. 871C>T (p. Gln291*) variation of the ACAN gene was the disease-causing variant in this family. Collectively, our newly discovered mutation expanded the spectrum of ACAN gene mutations.

Novel missense ACAN gene variants linked to familial osteochondritis dissecans cluster in the C-terminal globular domain of aggrecan

The cartilage aggrecan proteoglycan is crucial for both skeletal growth and articular cartilage function. A number of aggrecan (ACAN) gene variants have been linked to skeletal disorders, ranging from short stature to severe chondrodyplasias. Osteochondritis dissecans is a disorder where articular cartilage and subchondral bone fragments come loose from the articular surface. We previously reported a missense ACAN variant linked to familial osteochondritis dissecans, with short stature and early onset osteoarthritis, and now describe three novel ACAN gene variants from additional families with this disorder. Like the previously described variant, these are autosomal dominant missense variants, resulting in single amino acid residue substitutions in the C-type lectin repeat of the aggrecan G3 domain. Functional studies showed that neither recombinant variant proteins, nor full-length variant aggrecan proteoglycan from heterozygous patient cartilage, were secreted to the same level as wild-type aggrecan. The variant proteins also showed decreased binding to known cartilage extracellular matrix ligands. Mapping these and other ACAN variants linked to hereditary skeletal disorders showed a clustering of osteochondritis dissecans-linked variants to the G3 domain. Taken together, this supports a link between missense ACAN variants affecting the aggrecan G3 domain and hereditary osteochondritis dissecans.

Exploring the genetic causes of isolated short stature. What has happened to idiopathic short stature?

Statural growth is underpinned by development of the growth plate during the process of endochondral ossification, which is strongly regulated by numerous local factors (intracellular, paracrine and extracellular matrix factors) and systemic factors (nutrition, hormones, proinflammatory cytokines and extracellular fluids). This explains why growth retardation can be associated with numerous pathologies, particularly genetic syndromes, hormonal or inflammatory conditions, or gastrointestinal disorders having a nutritional impact. However, in most cases (80%), no specific aetiology is found after clinical investigation and conventional additional tests have been carried out. In such cases, "idiopathic" short stature is diagnosed, which includes patients presenting with constitutional delay of growth and development and familial short stature, but also patients with very subtle constitutional skeletal dysplasia which are not easily identifiable. In recent years, new methods of genetic investigation (e.g. gene panels, exome or genome sequencing) have made it possible to identify many genetic variants associated with apparently isolated short stature. Indeed, it is still difficult to estimate the proportion of patients presenting with idiopathic short stature for which a molecular diagnosis of monogenic conditions could be made. This estimate varies hugely depending on the thoroughness of the clinical, laboratory and radiological assessments performed prior to molecular analysis, since retrospective analysis of positive cases usually reveals subtle signs of underlying syndromes or rare skeletal disorders. Molecular diagnosis in children is important to be able to offer genetic counselling and to organise patient management. Moreover, improved understanding of the molecular basis of these cases of short stature opens up numerous possibilities for more specific treatments targeting the growth plate. © 2022 French Society of Pediatrics. Published by Elsevier Masson SAS. All rights reserved.

Single-Cell Gene Expression Analysis in Patients with Medullary Sponge Kidney and a Retrospective Study

OBJECTIVE

To establish better diagnosis thinking and provide advanced understanding of MSK, the CT imaging features, clinical characteristics, and the expression of suspected genes in the kidney spatiotemporal immune zonation and fetal renal development were investigated.

METHODS

17 patients with MSK hospitalized in our hospital were selected as our research subjects. Human Phenotype Ontology, MalaCards: The Human Disease Database, GeneCards: The Human Gene Database, Human Protein Atlas, and Single Cell Expression Atlas were used to analyze this disease.

RESULTS

In our 17 patients, the incidence of MSK tended to be the same in male and female, and the onset age of MSK was probably 31-50 years old. The top one related disease of MSK was nephrocalcinosis and the most frequent phenotype related to MSK was nephrolithiasis. In addition, the expression of HNF1B, CLCN5, GDNF, ATP6V0A4, ATP6V1B1, LAMA2, RET, ACAN, and ABCC8 has been implicated in both human kidney immune zonation and fetal kidney development.

CONCLUSIONS

HNF1B, CLCN5, GDNF, ATP6V0A4, ATP6V1B1, LAMA2, RET, ACAN, and ABCC8 could be independent indicators for the diagnosis and preventive intervention of MSK patients, and abnormal kidney development due to mutations in key genes was the underlying cause of MSK.

Description of the molecular and phenotypic spectrum in Chinese patients with aggrecan deficiency: Novel ACAN heterozygous variants in eight Chinese children and a review of the literature

OBJECTIVE

This study analyzed eight Chinese short stature children with aggrecan deficiency, and aimed to investigate potential genotype-phenotype correlations, differences in clinical characteristics between the Chinese and the Western populations, and effectiveness of recombinant human growth hormone therapy in patients with ACAN variants through a review of the literature.

METHODS

Pediatric short stature patients with ACAN heterozygous variants were identified using whole-exome sequencing. Subsequently, a literature review was carried out to summarize the clinical features, genetic findings, and efficacy of growth-promoting therapy in patients with ACAN variants.

RESULTS

We identified seven novel ACAN mutations and one recurrent variant. Patients in our center manifested with short stature (average height SDS: -3.30 ± 0.85) with slight dysmorphic characteristics. The prevalence of dysmorphic features in the Chinese populations is significantly lower than that in the Western populations. Meanwhile, only 24.24% of aggrecan-deficient Chinese children showed significantly advanced bone age (BA). Promising therapeutic benefits were seen in the patients who received growth-promoting treatment, with an increase in growth velocity from 4.52 ± 1.00 cm/year to 8.03 ± 1.16 cm/year.

CONCLUSION

This study further expanded the variation spectrum of the ACAN gene and demonstrated that Chinese children with short stature who carried ACAN heterozygous variants exhibited early growth cessation, which may remain unnoticed by clinicians as most of these children had very mild dysmorphic characteristics and showed BA that was consistent with the chronological age. Genetic testing may help in the diagnosis.

Evaluation of Growth Hormone Therapy in Seven Chinese Children With Familial Short Stature Caused by Novel ACAN Variants

OBJECTIVE

ACAN gene variants are an important cause of familial short stature (FSS). Appropriate growth-promoting therapies effectively improve the patient height. Here, we report a therapeutic assessment of cases of seven families of FSS patients with heterozygous ACAN variants. Our findings provide a valuable theoretical basis for the clinical diagnosis and treatment of this disease.

METHODS

From December 2020 to June 2021, 32 FSS patients were examined in Tianjin Medical University General Hospital (Tianjin, China) by whole-exome sequencing to determine whether ACAN variants were present. Their clinical data were summarized and scrupulously analyzed.

RESULTS

We found seven novel heterozygous ACAN variants: c.1051 + 2T > A, c.313T > C (p.S105P), c.2660C > G (p.S887X), c.2153C > A (p. T718K), c.7243delG (p.D2415Tfs^*4), c.2911G > T (p.G971X), c.758-7T > C. All seven patients had proportionate short stature and mild skeletal dysplasia. Endocrine examination results were normal. Only one of the patients had an advanced bone age (1.1 years older than chronological age), whereas the other patients had normal bone ages. All of them had a family history of short stature, with or without osteoarthritis or intervertebral disc disease. All seven patients accepted treatment with recombinant human growth hormone (rhGH) and were regularly followed up. One patient did not come at the follow-up visit. The height of the remaining six patients before and after the treatment was -2.89 ± 0.68 SDS, -1.91 ± 0.93 SDS, respectively, with a treatment course of 1.85 ± 1.91 years. A good therapeutic response was observed in all of them.

CONCLUSIONS

In this study, seven novel heterozygous variants in ACAN were discovered, which expanded the spectrum of the already established ACAN pathogenic variants. In FSS cohort, the proportion of ACAN variants accounted was large. The treatment with rhGH effectively increased the patient height, but further studies with longer follow-up periods and more extensive observations are required to elucidate the long-term effect.

Identification of novel ACAN mutations in two Chinese families and genotype-phenotype correlation in patients with 74 pathogenic ACAN variations

Background

ACAN (OMIM 155760) is located on chromosome 15q26 and encodes the production of aggrecan. Aggrecan is a large chondroitin sulfate proteoglycan with a molecular weight of 254 kDa and contains 2530 amino acids. It is a critical structural component of the extracellular matrix of cartilage, including growth plate, articular, and intervertebral disk cartilage. It plays a key role in bone development.

Methods

Here, we describe two pedigrees with loss‐of‐function variants in ACAN. Whole exome sequencing was performed for the probands from each family. We illustrate the clinical variability associated with ACAN variants.

Results

The proband of pedigree A manifested short stature, relative macrocephaly, mild flat nasal bridge, low‐set ears, short neck, and short thumbs. The proband of pedigree B had short height, abnormal vertebral development, and central precocious puberty. By trio‐based whole exome sequencing and in silico analyses, we identified two de novo heterozygous variants of ACAN: NM_013227.4: c.116dupT, p.Arg40Glufs*51 and NM_013227.4: c.2367delC, p.Ser790Glnfs*20 (accession number: AC103982.10).

Conclusion

The clinical manifestations of ACAN gene variants are diverse. ACAN gene variants are important genetic factors for short stature and should be considered as the differential diagnosis of children with idiopathic short stature (ISS).

Retrospective Diagnosis of a Novel ACAN Pathogenic Variant in a Family With Short Stature: A Case Report and Review of the Literature

Short stature is a frequent disorder in the pediatric population and can be caused by multiple factors. In the last few years, the introduction of Next Generation Sequencing (NGS) in the molecular diagnostic workflow led to the discovery of mutations in novel genes causing short stature including heterozygous mutations in ACAN gene. It encodes for aggrecan, a primary proteoglycan component specific for the structure of the cartilage growth plate, articular and intervertebral disc. We report a novel ACAN heterozygous pathogenic variant in a family with idiopathic short stature, early-onset osteoarthritis and osteoarthritis dissecans (SSOAOD). We also performed a literature review summarizing the clinical characteristic of ACAN's patients. The probands are two Caucasian sisters with a family history of short stature and osteoarthritis dissecans. They showed dysmorphic features such as mild midface hypoplasia, brachydactyly and broad thumbs, especially the great toes. The same phenotype was presented in the mother who had had short stature and suffered from intervertebral disc disease. DNA sequencing identified a heterozygous pathogenic variation (c.4390delG p.Val1464Ter) in the sisters, with a maternal inheritance. The nonsense mutation, located on exon 12, results in premature truncation and presumed loss of protein function. In terms of treatment, our patients underwent recombinant human growth hormone replacement therapy, associated with gonadotropin releasing hormone therapy, in order to block early growth cessation and therefore reach a better final height. Our case suggests that SSOAOD ACAN related should be considered in the differential diagnosis of children with autosomal dominant short stature and family history of joints disease.

A wide range of protective and predisposing variants in aggrecan influence the susceptibility for otosclerosis

In this study, we investigated the association of ACAN variants with otosclerosis, a frequent cause of hearing loss among young adults. We sequenced the coding, 5'-UTR and 3'-UTR regions of ACAN in 1497 unrelated otosclerosis cases and 1437 matched controls from six different subpopulations. The association between variants in ACAN and the disease risk was tested through single variant and gene-based association tests. After correction for multiple testing, 14 variants were significantly associated with otosclerosis, ten of which represented independent association signals. Eight variants showed a consistent association across all subpopulations. Allelic odds ratios of the variants identified four predisposing and ten protective variants. Gene-based tests showed an association of very rare variants in the 3'-UTR with the phenotype. The associated exonic variants are all located in the CS domain of ACAN and include both protective and predisposing variants with a broad spectrum of effect sizes and population frequencies. This includes variants with strong effect size and low frequency, typical for monogenic diseases, to low effect size variants with high frequency, characteristic for common complex traits. This single-gene allelic spectrum with both protective and predisposing alleles is unique in the field of complex diseases. In conclusion, these findings are a significant advancement to the understanding of the etiology of otosclerosis.

Genetic evaluation in children with short stature

PURPOSE OF REVIEW

Short stature is a common clinical manifestation in children. Yet, a cause is often unidentifiable in the majority of children with short stature by a routine screening approach. The purpose of this review is to describe the optimal genetic approach for evaluating short stature, challenges of genetic testing, and recent advances in genetic testing for short stature.

RECENT FINDINGS

Genetic testing, such as karyotype, chromosomal microarray, targeted gene sequencing, or exome sequencing, has served to identify the underlying genetic causes of short stature. When determining which short stature patient would benefit from genetic evaluation, it is important to consider whether the patient would have a single identifiable genetic cause. Specific diagnoses permit clinicians to predict responses to growth hormone treatment, to understand the phenotypic spectrum, and to understand any associated co-morbidities.

SUMMARY

The continued progress in the field of genetics and enhanced capabilities provided by genetic testing methods expands the ability of physicians to evaluate children with short stature for underlying genetic defects. Continued effort is needed to elaborate new genetic causes of linear growth disorders, therefore, we expand the list of known genes for short stature, which will subsequently increase the rate of genetic diagnosis for children with short stature.

A High Proportion of Novel ACAN Mutations and Their Prevalence in a Large Cohort of Chinese Short Stature Children

CONTEXT

Aggrecan, encoded by the ACAN gene, is the main proteoglycan component in the extracellular cartilage matrix. Heterozygous mutations in ACAN have been reported to cause idiopathic short stature. However, the prevalence of ACAN pathogenic variants in Chinese short stature patients and clinical phenotypes remain to be evaluated.

OBJECTIVE

We sought to determine the prevalence of ACAN pathogenic variants among Chinese short stature children and characterize the phenotypic spectrum and their responses to growth hormone therapies.

PATIENTS AND METHODS

Over 1000 unrelated short stature patients ascertained across China were genetically evaluated by next-generation sequencing-based test.

RESULT

We identified 10 novel likely pathogenic variants and 2 recurrent pathogenic variants in this cohort. None of ACAN mutation carriers exhibited significant dysmorphic features or skeletal abnormities. The prevalence of ACAN defect is estimated to be 1.2% in the whole cohort; it increased to 14.3% among those with advanced bone age and to 35.7% among those with both advanced bone age and family history of short stature. Nonetheless, 5 of 11 ACAN mutation carries had no advanced bone age. Two individuals received growth hormone therapy with variable levels of height SD score improvement.

CONCLUSION

Our data suggest that ACAN mutation is 1 of the common causes of Chinese pediatric short stature. Although it has a higher detection rate among short stature patients with advanced bone age and family history, part of affected probands presented with delayed bone age in Chinese short stature population. The growth hormone treatment was moderately effective for both individuals.

The Link between Aggrecan and Familial Osteochondritis Dissecans

Osteochondritis dissecans (OCD) is a chronic disease of the articular cartilage characterized by focal lesions of subchondral bone and overlaying cartilage. Through the growing number of reports describing the high prevalence of OCD in some families, the subcategory termed familial OCD (FOCD) was established. With the development of genetic approaches such as genome-wide association studies and sequencing, aggrecan (ACAN) has been identified as one of the genes of interest associated with FOCD. Aggrecan is a crucial protein for the preservation and function of cartilage. However, due to FOCD being characterized relatively recently, there is a paucity of literature on the subject. The purpose of this review is to explore the relationship between ACAN mutations and familial OCD as well as to explore current treatment options and avenues for future research. In vitro and animal studies have shown the importance of ACAN in the preservation of cartilage. However, the only human ACAN mutation related to OCD ever identified is a V2303M mutation in the G3 domain. Multiple treatments have been superficially explored, and some options such as growth hormone (GH) and gonadotrophin-releasing hormone agonists (GnRHa) show potential. Thus, further research on FOCD in needed to identify other ACAN mutations and determine optimal treatment modalities for this patient population.