ACAN Mutations Research Articles

THU160 A Prospective Genetic Analysis Of Children With Idiopathic Short Stature (ISS) Using Whole-exome Sequencing (WES): First Results

Abstract Disclosure: L.D. Cellin: None. N.L. Menezes De Andrade: None. R.C. Rezende: None. V. Souza: None. N.C. Dantas: None. E. Quedas: None. M.F. Funari: None. G. Vasques: None. R.D. Scalco: None. A.C. Malaquias: None. A. Jorge: Consulting Fee; Self; Novo Nordisk. Grant Recipient; Self; BioMarin. Introduction: Children classified as idiopathic short stature (ISS) may have a monogenic cause that can explain their growth disorder. In this context, genetic tests emerge as a new diagnostic tool. Objectives: To determine the usefulness of WES for the genetic investigation of children with ISS. Patients and Methods: We sequentially enrolled 95 children with ISS without previous genetic testing, except for karyotyping for girls. In WES analysis, we prioritized rare variants (MAF<0.001), classified as loss-of-function (LoF) or missense predicted to be deleterious on in silico predictions. All variants were categorized according to ACMG/AMP criteria. We analyzed genes previously associated with growth disorders. CNV analysis was performed based on WES data; additionally, MLPA for SHOX was performed to assess deletion in regulatory regions. In positive cases, we carry out segregation in the family. Results: Our cohort was characterized by male preponderance (67%), markedly short stature (height SDS -2.6±0.7, 20% with height SDS<-3), and in 48% of cases, at least one of the parents have short stature. We identified 12 pathogenic or likely pathogenic (P/LP) variants by WES, including two gene deletions (SHOX and PTHLH) and 10 point mutations in ACAN (2x), IHH, PRKG2, LTBP3, ERF, THRA, GHR, PTPN11, and NF1. Additionally, two deletions involving the regulatory region of the SHOX gene were identified by MLPA. One patient had two P/LP alterations, totaling a diagnostic yield of 13.7% (12.6% if only WES results were considered). It is noteworthy that in addition to genes already associated with ISS (ACAN, SHOX, IHH, GHR, PTPN11, NF1), we observed a greater diversity of genes, including resistance to thyroid hormones (THRA) and milder forms of skeletal dysplasia (LTBP3, PTHLH, PRKG2). All but one of the variants were in the heterozygous state, including two de novo variants and four inherited from a parent with short stature. Fifteen patients have variants of uncertain significance (VUS) in genes already associated with growth disorder: IHH (3x), FGFR3 (2x), NPR2 (2x), LZTR1 (2x), MMP13, COL11A1, COL11A2, EXT2, IGF1R, and WNT5. Furthermore, four patients have variants of interest in new candidate genes (MAU2, MAP3K4, NR2E1, C6ORF136). Conclusion: The diagnostic yield was similar to other studies in children with ISS, but a greater diversity of genetic causes was observed, with those involving growth-plate genes and the RAS-MAPK pathway being more frequent. The large number of VUS highlights the need for further studies and new tools to classify these variants definitively. Presentation: Thursday, June 15, 2023

Downregulation of ACAN is Associated with the Growth hormone pathway and Induces short stature.

ACAN heterozygous mutations can cause short stature in patients with or without advanced bone age and have recently attracted researchers' attention. Growth hormone can be used to treat short stature induced by ACAN mutations; however, few studies have focused on the underlying mechanism of this treatment. Four patients with new mutations were reported based on clinical data and genetic tests. We investigated the expression and Gene Ontology biological process enrichment of ACAN and GH pathways based on GTEx databases through bioinformatics analyses. The effect of ACAN on the growth hormone response evaluated in ATDC5 cells with a growth hormone stimulation test. Four mutations were reported in this study: c.619C > A, c.1967A > G, c.1888G > A, and c.1308_1309del. All patients' heights were under -2.5 SD, with one had advanced bone age, and two had GH deficiency. Two individuals received growth hormone therapy acquired variable levels of height SD score improvement. ACAN and the GH pathway were strongly associated; ACAN does not affect GHR but regulates the response to GH. Downregulating ACAN inhibited ATDC5 cell proliferation induced by GH. ACAN is associated with the GH pathway, revealing the potential mechanism underlying GH-targeted treatment for ACAN mutation-induced short stature. GH-promoting therapies may increase patients' heights.

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.

Clinical phenotype and musculoskeletal characteristics of patients with aggrecan deficiency.

Aggrecan is a proteoglycan within the physeal and articular cartilage. Aggrecan deficiency, due to heterozygous mutations in the ACAN gene, causes dominantly inherited short stature and, in many patients, early-onset osteoarthritis and degenerative disc disease. We aimed to further characterize this phenotypic spectrum with an emphasis on musculoskeletal health. Twenty-two individuals from nine families were enrolled. Histories and examinations focused on joint health, gait analysis, joint specific patient reported outcomes, and imaging studies were performed. All patients had dominantly inherited short stature, with the exception of a de novo mutation. Short stature was worse in adults versus children (median height -3.05 SD vs. -2.25 SD). ACAN mutations were not always associated with bone age advancement (median advancement +1.1 years, range 0 to +2 years). Children had subtle disproportionality and clinically silent joint disease-25% with osteochondritis dissecans (OD). Adults had a high prevalence of joint symptomatology-decline in knee function, disability from spinal complaints, and lower physical activity on outcome measures. Osteoarthritis (OA) and OD was detected in 90% of adults, and orthopedic surgeries were reported in 60%. Aggrecan deficiency leads to short stature with progressive decline in height SD, mild skeletal dysplasia, and increasing prevalence of joint pathology over time. Optimal musculoskeletal health and quality of life can be attained with timely identification of pathology and intervention.

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

ContextAggrecan, 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.ObjectiveWe 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 MethodsOver 1000 unrelated short stature patients ascertained across China were genetically evaluated by next-generation sequencing–based test.ResultWe 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.ConclusionOur 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.

Growth-Promoting Therapies May Be Useful In Short Stature Patients With Nonspecific Skeletal Abnormalities Caused By Acan Heterozygous Mutations: Six Chinese Cases And Literature Review

There are numerous reasons for short stature, including mutations in osteochondral development genes. ACAN, one such osteochondral development gene in which heterozygous mutations can cause short stature, has attracted attention from researchers in recent years. Therefore, we analyzed six cases of short stature with heterozygous ACAN mutations and performed a literature review. Clinical information and blood samples from 6 probands and their family members were collected after consent forms were signed. Gene mutations in the probands were detected by whole-exome sequencing. Then, we searched the literature, performed statistical analyses, and summarized the characteristics of all reported cases. We identified six novel mutations in ACAN: c.1411C>T, c.1817C>A, c.1762C>T, c.2266G>C, c.7469G>A, and c.1733-1G>A. In the literature, more than 200 affected individuals have been diagnosed genetically with a similar condition (height standard deviation score &lsqb;SDS] -3.14 ± 1.15). Among affected individuals receiving growth-promoting treatment, their height before and after treatment was SDS -2.92±1.07 versus SDS -2.14±1.23 (P<.001). As of July 1, 2019, a total of 57 heterozygous ACAN mutations causing nonsyndromic short stature had been reported, including the six novel mutations found in our study. Approximately half of these mutations can lead to protein truncation. This study used clinical and genetic means to examine the relationship between the ACAN gene and short stature. To some extent, clear diagnosis is difficult, since most of these affected individuals' characteristics are not prominent. Growth-promoting therapies may be beneficial for increasing the height of affected patients. AI = aromatase inhibitor; ECM = extracellular matrix; GnRHa = gonadotropin-releasing hormone analogue; IQR = interquartile range; MIM = Mendelian Inheritance in Man; PGHD = partial growth hormone deficiency; rhGH = recombinant human growth hormone; SDS = standard deviation score; SGA = small for gestational age; SGHD = severe growth hormone deficiency.

Mutations of uncertain significance in heterozygous variants as a possible cause of severe short stature: a case report

BackgroundLinear bone growth is achieved by the division of chondrocytes at the growth plate and is regulated by endocrine and paracrine factors such as growth hormone. Mutations that negatively affect chondrogenesis can be a contributor to short stature. One such mutation can occur in the ACAN gene, causing short stature and advanced bone age. Similarly, mutations in growth hormone receptors (GHR) can lead to Laron syndrome (LS), one of the several disorders that are collectively called growth hormone insensitivity syndrome (GHI). Another example is Floating-Harbor syndrome (FHS), a rare autosomal dominant due to mutations in the SRCAP gene that can also result in short stature.Case presentationWe report the case of a 6-year-old female with concomitant mutations in the three genes mentioned above. The mutations reported here were found on genetic studies and are usually benign, causing a variant of undetermined significance. However, our patient’s phenotype could only be explained by the compounded effects of pathogenic mutations of these genes. Some of the same mutations were also found in the patient’s father and her paternal grandfather. Both also presented with short stature, though not to the same degree as our patient. While these mutations are often reported to be insignificant, they gave rise to severe short stature and a specific phenotype in the patient when presented together. We think that even though the GHI spectrum is inherited through an autosomal recessive pattern, the sum of these heterozygous mutations resulted in severe short stature despite the limited GHI seen in our patient, the father, and the grandfather, through a rare ACAN and SRCAP mutation that, to our knowledge, has not been previously reported as a pathogenic mutation in the literature.ConclusionWe investigated the possible synergistic effects of these variations on exacerbation or masking of the signs and symptoms of GHI with the hope of providing a better understanding of these genes and their function through our rare case.

Cross-sectional Evaluation Of Musculoskeletal Outcomes &amp; Physical Activity Levels In Patients With Aggrecan Deficiency

PURPOSE: Aggrecan is a key proteoglycan found in the extracellular matrix of articular and physeal cartilage and provides resistance to compression and deformity. Aggrecan deficiency is a recently described autosomal dominantly inherited condition due to mutations in the ACAN gene. Individuals with aggrecan deficiency experience premature growth cessation, short stature, and advanced skeletal maturation. Proteoglycan loss has been associated with osteoarthritis and degenerative joint disease. This study examines the joint manifestations of a cohort of prepubertal patients and affected family members with Aggrecan deficiency. METHODS: Probands (ACAN mutation, bone age ≥ chronological age, normal IGF-I) and affected relatives underwent baseline joint evaluation including history and physical exam, quality of life, physical activity (Marx), joint specific outcomes (Pedi-IKDC, Oswestry), and radiographic assessment (knee x-ray and MRI). RESULTS: Twenty subjects (9 male, 11 female, ages 2.4-62.6 years) were enrolled in the study. The average Pedi-IKDC of the pediatric subjects (mean age 6.5+/-3.2 years, range 2.4-12.5 years) was 95.5+/-8.9 compared to 74.9+/-20.1 for adult subjects (mean age 42.9+/-10.6 years, range 25.4-62.6 years), (p=0.02). The average Marx activity score was 12.2+/-2.2 for pediatric subjects compared to 2.6+/-4.4 for the adults (p<0.001).Two pediatric subjects reported a history of knee pain while none reported back or other musculoskeletal concerns. Additionally, two pediatric subjects were identified with osteochondral defects on MRI while 2 others displayed variant MRI findings. Of the 9 adults, 67% reported knee pain (4 patellar dislocations), 88% displayed osteoarthritis on knee x-ray, 67% reported other joint concerns, and 56% reported back pain. Seven orthopedic surgeries were reported. CONCLUSIONS: Patients with ACAN deficiency appear to be at high risk of premature joint complications as evidenced by (1) the high rate of knee, back, and joint complaints, (2) increased requirement for surgical intervention, and (3) low physical activity scores. Early surveillance of joint complaints, lifestyle counseling and therapeutic interventions to improve joint health and maintain physical activity should be considered to optimize patient outcomes and quality of life.

Small stature with osteochondritis: a clinical report of a family with ACAN mutation and review of the literature

Searchable abstracts of presentations at key conferences in endocrinology ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

A recessive lethal chondrodysplasia in a miniature zebu family results from an insertion affecting the chondroitin sulfat domain of aggrecan

BackgroundCongenital skeletal malformations represent a heterogeneous group of disorders affecting bone and cartilage development. In cattle, particular chondrodysplastic forms have been identified in several miniature breeds. In this study, a phenotypic characterization was performed of an affected Miniature Zebu calf using computed tomography, necropsy and histopathological examinations, whole genome sequencing of the case and its parents on an Illumina NextSeq 500 in 2 × 150 bp paired-end mode and validation using Sanger sequencing and a Kompetitive Allele Specific PCR assay. Samples from the family of an affected Miniature Zebu with bulldog syndrome including parents and siblings, 42 healthy Miniature Zebu not related with members of the herd and 88 individuals from eight different taurine cattle breeds were available for validation.ResultsA bulldog-like Miniature Zebu calf showing a large bulging head, a short and compressed body and extremely short and stocky limbs was delivered after a fetotomy. Computed tomography and necropsy revealed severe craniofacial abnormalities including a shortening of the ventral nasal conchae, a cleft hard palate, rotated limbs as well as malformed and fused vertebrae and ribs. Histopathologic examination showed a disorganization of the physeal cartilage with disorderly arranged chondrocytes in columns and a multifocal closed epiphyseal plate. Whole-genome sequencing of this malformed Miniature Zebu calf, its dam and sire and subsequent comparative sequence analysis revealed a one base pair insertion (ACAN:c.5686insC) located within the cartilage development gene aggrecan (ACAN) exclusively homozygous in the affected calf and heterozygous in its parents. This variant was predicted to cause a frameshift (p.Val1898fsTer9) and thus a truncation of the chondroitin sulfate domain as well as a loss of the C-terminal globular domain of ACAN. It perfectly co-segregated with the lethal bulldog syndrome in Miniature Zebus.ConclusionsWe found a novel mutation in ACAN causing a recessive lethal chondrodysplasia in Miniature Zebu cattle. A diagnostic test for this mutation is now available for Miniature Zebu breeders preventing further cases of bulldog syndrome by targeted matings. To the authors’ best knowledge, this is the first case of a Miniature Zebu associated with an ACAN mutation.

Genetic screening confirms heterozygous mutations in ACAN as a major cause of idiopathic short stature

Short stature is a common pediatric disorder affecting 3% of the population. However, the clinical variability and genetic heterogeneity prevents the identification of the underlying cause in about 80% of the patients. Recently, heterozygous mutations in the ACAN gene coding for the proteoglycan aggrecan, a main component of the cartilage matrix, were associated with idiopathic short stature. To ascertain the prevalence of ACAN mutations and broaden the phenotypic spectrum in patients with idiopathic short stature we performed sequence analyses in 428 families. We identified heterozygous nonsense mutations in four and potentially disease-causing missense variants in two families (1.4%). These patients presented with a mean of −3.2 SDS and some suggestive clinical characteristics. The results suggest heterozygous mutations in ACAN as a common cause of isolated as well as inherited idiopathic short stature.

Genetic screening confirms heterozygous mutations in ACAN as a major cause of idiopathic short stature

Short stature is a common pediatric disorder affecting 3% of the population. However, the clinical variability and genetic heterogeneity prevents the identification of the underlying cause in about 80% of the patients. Recently, heterozygous mutations in the ACAN gene coding for the proteoglycan aggrecan, a main component of the cartilage matrix, were associated with idiopathic short stature. To ascertain the prevalence of ACAN mutations and broaden the phenotypic spectrum in patients with idiopathic short stature we performed sequence analyses in 428 families. We identified heterozygous nonsense mutations in four and potentially disease-causing missense variants in two families (1.4%). These patients presented with a mean of −3.2 SDS and some suggestive clinical characteristics. The results suggest heterozygous mutations in ACAN as a common cause of isolated as well as inherited idiopathic short stature.

Novel pathogenic ACAN variants in non-syndromic short stature patients

BackgroundPathogenic variants of ACAN have been reported to cause spondyloepiphyseal dysplasia Kimberley type, spondyloepimetaphyseal dysplasia, familial osteochondritis dissecans and idiopathic short stature with normal to advanced bone age. A recent international cohort study significantly expanded the ACAN mutation spectrum, further delineated the heterogeneous clinical characteristics of ACAN mutation patients. The prevalence of ACAN mutation in short stature patients is yet unknown. MethodsHere we set to assess the frequency of ACAN variants among a cohort of 218 Chinese children with non-syndromic short stature. ResultsWe identified three novel truncating variants at the 5′ end of ACAN gene. All these pathogenic variants co-segregate with severe short stature phenotype in families. In addition, none of the probands showed significant advanced bone age. All affected individuals showed no signs of significant dysmorphic features or skeletal abnormities. The prevalence of ACAN defect in this cohort is estimated to be 1.4% (3/218). It is higher among families with parents also affected with severe short stature, up to 7.0% (3/43) if parental height is <2.5 SD or 16.7% (3/18) if parental height is <3.0 SD. ConclusionOur data suggest that ACAN mutation is a relative common cause of familial severe short stature.

Identification of a novel heterozygous mutation of the Aggrecan gene in a family with idiopathic short stature and multiple intervertebral disc herniation

Aggrecan is a critical proteoglycan component of the extracellular matrix of the growth plates and articular cartilage and has a key role in the biophysical and biomechanical properties of cartilage. Recently, heterozygous mutations in the ACAN gene, which encodes aggrecan, have been identified in patients with short stature and accelerated bone age. We herein report another family with a heterozygous ACAN mutation associated with idiopathic short stature along with accelerated bone age and early-onset herniation of the lumbar discs at the levels of L1/2 through L5/S1. Whole-exome sequencing identified a novel heterozygous frameshift mutation in the ACAN gene (c.1744delT; p.Phe582fs*69) in all of the affected family members but not in the unaffected one, providing further evidence that ACAN haploinsufficiency causes short stature with advanced bone maturation. In addition, we advocate early-onset multiple disc herniation as a novel phenotype associated with ACAN haploinsufficiency.

Next generation sequencing-based mutation screening of 86 patients with idiopathic short stature

Although mutations in ACAN, FGFR3, NPR2, and SHOX typically lead to skeletal dysplasia, and mutations in GHRHR, GH1, GHR, STAT5B, IGF1, IGFALS, and IGF1R usually underlie hormonal defects of the growth hormone (GH)-insulin-like growth factor 1 (IGF1) axis, such mutations have also been identified in patients with idiopathic short stature (ISS). Of these, SHOX abnormalities are known to account for a certain percentage of ISS cases, whereas the frequency of mutations in the other 10 genes in ISS cohorts remains unknown. Here, we performed next-generation sequencing-based mutation screening of the 10 genes in 86 unrelated Japanese ISS patients without SHOX abnormalities. We searched for rare protein-altering variants. The functional significance of the identified variants was assessed by in silico analyses. Consequently, we identified 18 heterozygous rare variants in 19 patients, including four probable damaging variants in ACAN, six pathogenicity-unknown variants in FGFR3, GHRHR, GHR, and IGFALS, and eight possible benign variants. Pathogenic variants in NPR2, GH1, and IGF1 were absent from our cohort. Unlike previously reported patients with ACAN mutations, our four patients with ACAN variants manifested non-specific short stature with age-appropriate or mildly delayed bone ages, and had parents of normal stature. These results indicate that ACAN mutations can underlie ISS without characteristic skeletal features, and that such mutations are possibly associated with de novo occurrence or low penetrance. In addition, our data imply that mutations in FGFR3, NPR2, and GH-IGF1 axis genes play only limited roles in the etiology of ISS.

ACAN mutations as a cause of familial short stature.

.Aggrecan, encoded by ACAN, is a major proteoglycan component of the extracellular matrix in the growth plate and articular cartilage. Aggrecan provides the hydrated gel structure important for the load-bearing properties of joints and plays a key role in cartilage and bone morphogenesis. At least 25 pathological ACAN mutations have been identified in patients with highly variable phenotypes of syndromic or non-syndromic short stature. This review provides an overview of the current understanding of ACAN and the clinical and genetic findings concerning aggrecan-associated diseases.

The aggrecanopathies; an evolving phenotypic spectrum of human genetic skeletal diseases.

The large chondroitin sulphated proteoglycan aggrecan (ACAN) is the most abundant non-collagenous protein in cartilage and is essential for its structure and function. Mutations in ACAN result in a broad phenotypic spectrum of non-lethal skeletal dysplasias including spondyloepimetaphyseal dysplasia, spondyloepiphyseal dysplasia, familial osteochondritis dissecans and various undefined short stature syndromes associated with accelerated bone maturation. However, very little is currently known about the disease pathways that underlie these aggrecanopathies, although they are likely to be a combination of haploinsufficiency and dominant-negative (neomorphic) mechanisms. This review discusses the known human and animal aggrecanopathies in the context of clinical presentation and potential disease mechanisms.

Identification of Novel Germline Variants in Early-Onset Familial Classical Hodgkin Lymphoma with Exome Sequencing

Hodgkin lymphoma (HL) is a malignancy of the lymphatic system that stems from germinal center B-cells. The global annual incidence of HL is 3 in 100,000, and it accounts for about 30% of all lymphomas. HL is further divided into four distinct subtypes, of which the classical Hodgkin lymphoma (cHL) constitutes 95 % of cases.The etiology of cHL is not completely understood. There is strong evidence from epidemiological and molecular biology studies that Epstein-Barr virus infection is associated with cHL pathogenesis. Indeed, about 40% of cHL cases are Epstein-Barr virus (EBV) positive, i.e. they express EBV-encoded RNAs. The role of genetic factors is also acknowledged: familial clustering of cHL has been reported. However, to date a germline translocation affecting KLHDC8B gene is the only known candidate for a penetrant cHL predisposing mutation.In this work, we studied a family of Middle-Eastern origin in which three out of five children were diagnosed with Epstein-Barr virus (EBV) positive cHL within a 6-year period. We exome sequenced the genomic DNA of three siblings diagnosed with cHL during childhood, and analyzed their shared germline variants using a control set of 3891 samples. In the exome data, all affected siblings displayed a relatively high degree of homozygosity, providing evidence for recessive mode of inheritance. After filtering against controls, 35 shared variants, of which only one was homozygous, remained. The candidate variants were then prioritized using computational methods and their effect to protein function was predicted. This left us with thirteen novel variants: a homozygous 57 bp in-frame deletion in ACAN, a removal of stop codon in LY75-CD302, a nonsense mutation in KIAA0140, and ten missense-type single-nucleotide variants (SNV) predicted damaging by two different computational methods. From these, homozygous deletion in ACAN (encoding for aggrecan) emerges as a candidate mutation for recessive cHL susceptibility. The deletion identified in ACAN removes part of the repeat sequence as well as 9 amino acids from the unique sequence. ACAN has not been associated with tumorigenesis or tumor predisposition thus far but recent research has, however, suggested that noncellular tumor microenvironment components may promote the oncogenic effects of EBV. Recessive pattern of inheritance would also fit the pedigree structure and the relatively high degree of homozygosity observed in affected siblings.In this study, we identified several feasible candidate genes for cHL predisposition. The pedigree data, the overall variation data, and the homozygous ACAN mutation finding, are compatible with possible recessive inheritance, though other modes of inheritance cannot be excluded. The identified candidate genes provide a platform for validation studies in extended sets of familial cHL samples. Robust identification of additional mutations in families with this intriguing disease susceptibility phenotype would be a breakthrough in cHL risk prediction, and provide valuable clues to the molecular basis of Hodgkin lymphoma. DisclosuresNo relevant conflicts of interest to declare.

Bulldog dwarfism in Dexter cattle is caused by mutations in ACAN

Bulldog dwarfism in Dexter cattle is one of the earliest single-locus disorders described in animals. Affected fetuses display extreme disproportionate dwarfism, reflecting abnormal cartilage development (chondrodysplasia). Typically, they die around the seventh month of gestation, precipitating a natural abortion. Heterozygotes show a milder form of dwarfism, most noticeably having shorter legs. Homozygosity mapping in candidate regions in a small Dexter pedigree suggested aggrecan (ACAN) as the most likely candidate gene. Mutation screening revealed a 4-bp insertion in exon 11 (2266_2267insGGCA) (called BD1 for diagnostic testing) and a second, rarer transition in exon 1 (-198C>T) (called BD2) that cosegregate with the disorder. In chondrocytes from cattle heterozygous for the insertion, mutant mRNA is subject to nonsense-mediated decay, showing only 8% of normal expression. Genotyping in Dexter families throughout the world shows a one-to-one correspondence between genotype and phenotype at this locus. The heterozygous and homozygous-affected Dexter cattle could prove invaluable as a model for human disorders caused by mutations in ACAN.