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Telomere biology disorders (TBDs) present heterogeneously, ranging from infantile bone marrow failure associated with very short telomeres to adult-onset interstitial lung disease (ILD) with normal telomere length. Yield of genetic testing and phenotypic spectra for TBDs caused by the expanding list of telomere genes in adults remain understudied. Thus, we screened adults aged ≥18 years with a personal and/or family history clustering hematologic disorders and/or ILD enrolled on The University of Chicago Inherited Hematologic Disorders Registry for causative variants in 13 TBD genes. Sixteen (10%) of 153 probands carried causative variants distributed among TERT (n = 6), TERC (n = 4), PARN (n = 5), or RTEL1 (n = 1), of which 19% were copy number variants. The highest yield (9 of 22 [41%]) was in families with mixed hematologic and ILD presentations, suggesting that ILD in hematology populations and hematologic abnormalities in ILD populations warrant TBD genetic testing. Four (3%) of 117 familial hematologic disorder families without ILD carried TBD variants, making TBD second to only DDX41 in frequency for genetic diagnoses in this population. Phenotypes of 17 carriers with heterozygous PARN variants included 4 (24%) with hematologic abnormalities, 67% with lymphocyte telomere lengths measured by flow cytometry and fluorescence in situ hybridization at or above the 10th percentile, and a high penetrance for ILD. Alternative etiologies for cytopenias and/or ILD such as autoimmune features were noted in multiple TBD families, emphasizing the need to maintain clinical suspicion for a TBD despite the presence of alternative explanations.

Introduction: UDP N‐acetylglucosamine2‐epimerase/N‐acetylmannosamine‐kinase (GNE) gene mutations can cause mostly autosomal‐recessive myopathy with juvenile‐onset known as hereditary inclusion‐body myopathy (HIBM). Methods: We describe a family of a patient showing an unusual HIBM with both vacuolar myopathy and myositis without quadriceps‐sparing, hindering diagnosis. We show how genetic testing with functional assays, clinical transcriptome sequencing (RNA‐seq) in particular, helped facilitate both the diagnosis and a better understanding of the genotype‐phenotype relationship. Results: We identified a novel 7.08 kb pathogenic deletion upstream of GNE using array comparative genomic hybridization (aCGH) and a common Val727Met variant. Using RNA‐seq, we found only monoallelic (Val727Met‐allele) expression, leading to ~50% GNE reduction in muscle. Importantly, α‐dystroglycan is hypoglycosylated in the patient muscle, suggesting HIBM could be a “dystroglycanopathy.” Conclusions: Our study shows the importance of considering aCGH for GNE‐myopathies, and the potential of RNA‐seq for faster, definitive molecular diagnosis of unusual myopathies. Muscle Nerve, 2019

To avoid acquired variants found in the blood, cultured skin fibroblasts are a recommended DNA source for germline genetic testing in patients with hematologic disorders, but data are lacking regarding practicality and limitations. We conducted a retrospective cohort study of 350 subjects with hematologic disorders who underwent skin fibroblast culture for germline genetic testing. We analyzed nextgeneration sequencing data from the targeted capture of 144 inherited cancer and bonemarrow failure genes to identify variants at heterozygous and subclonal variant allele frequencies. Sixteen (5%) biopsies failed to culture. Culture failure was more likely in samples with delays in culture initiation (OR = 4.3; p < 0.01) or a pathogenic variant in a telomere gene (OR = 42.6; p < 0.01). Median culture time was 28 days (IQR 22−29 days). Culture time was longer for subjects with prior allogeneic stem cell transplantation (+10.7%; p = 0.02) and shorter in subjects with a heterozygous pathogenic variant (−11.9%; p < 0.01), larger biopsy size (−10.6%; p < 0.01), or lymphoid malignancy (−8.4%; p < 0.01). Subclonal variants were identified in 10 (4%) and confirmed in five (56%) of eight with alternate samples available. Subclonal and discordant variants illustrate that germline testing from cultured skin fibroblasts requires phenotypic correlation and, in rare cases, follow-up studies for optimal interpretation.

mini@ncbs.res.in.

The semaphorin protein family is a diverse set of extracellular signaling proteins that perform fundamental roles in the development and operation of numerous biological systems, notably the nervous, musculoskeletal, cardiovascular, endocrine, and reproductive systems. Recently, recessive loss‐of‐function (LoF) variants in SEMA3A (semaphorin 3A) have been shown to result in a recognizable syndrome characterized by short stature, skeletal abnormalities, congenital heart defects, and variable additional anomalies. Here, we describe the clinical and molecular characterization of a female patient presenting with skeletal dysplasia, hypogonadotropic hypogonadism (HH), and anosmia who harbors a nonsense variant c.1633C>T (p.Arg555*) and a deletion of exons 15, 16, and 17 in SEMA3A in the compound heterozygous state. These variants were identified through next‐generation sequencing analysis of a panel of 26 genes known to be associated with HH/Kallmann syndrome. Our findings further substantiate the notion that biallelic LoF SEMA3A variants cause a syndromic form of short stature and expand the phenotypic spectrum associated with this condition to include features of Kallmann syndrome.

Introduction Peripheral blood is the standard tissue source for germline genetic testing in most scenarios. In patients with hematologic malignancies, however, peripheral blood frequently contains tumor- or clonal hematopoiesis-related acquired genetic variants, often occurring in genes that can also cause inherited cancer susceptibility if present in the germline. Thus, an alternative tissue source is necessary. Cultured skin fibroblasts have been used as a potentially ideal alternative because they are free from blood contamination and provide ample DNA yields, advantages that other alternatives such as saliva or nail clippings lack. However, optimal culture methods, expected time from biopsy to sufficient DNA yield, culture failure rate, and limitations of this technique, including the possibility of variants being acquired solely due to the culturing process, are not yet known. Methods We conducted a retrospective cohort study of subjects with cytopenias or hematologic malignancies who underwent skin biopsy and fibroblast culture for germline genetic testing from April 2014 to June 2018. Skin biopsy culture technical data, including time from biopsy to culture set-up, shipment from an outside institution, culture failure, and biopsy size, were abstracted from tissue culture logs. Patient demographics, comorbidities, medication history, and hematologic diagnosis and treatment were abstracted from medical records. Next generation sequencing data from targeted capture of 144 inherited cancer and bone marrow failure predisposition genes obtained for clinical genetic testing purposes were analyzed to identify variants at both germline (40-60%) and subclonal (10-40%) variant allele frequencies (VAF). Pathogenicity was interpreted according to ACMG/AMP guidelines. Fisher's exact tests and logistic regression models were used to assess associations with culture failure. T-tests and linear regression models were used to assess factors associated with mean time to confluency. Results In total, we studied 350 samples from unique patients, including 61 (24%) who carried one or more pathogenic or likely pathogenic cancer susceptibility gene variant(s). Overall, 16 of the 350 (5%) biopsies failed to grow in culture. The median time from skin biopsy to sufficient growth to extract DNA for genetic testing was 27 days (IQR 22-29 days). Culture failure was significantly more likely in samples with a delay in culture initiation for 24 hours post biopsy (OR=4.32; p&lt;0.01), and a pathogenic germline variant in a gene associated with telomere maintenance (OR=64.50; p&lt;0.01). Factors associated with an increased mean time to sufficient growth included prior allogeneic stem cell transplant (32.1 days versus 27.2 days; p&lt;0.01) and prior intravenous (IV) steroid exposure (29.9 days versus 26.4 days; p&lt;0.01). Among samples cultured successfully, carriers of any pathogenic germline variant had a significantly decreased mean time to sufficient growth (25.4 days versus 28.6 days; p&lt;0.01). A pathogenic or likely pathogenic subclonal variant was identified in 11 (4%) subjects at a median VAF of 20%. Among eight of these with additional tissue available, the presence of the variant was confirmed in four (50%). In individual cases, we found evidence of loss of a pathogenic variant in the hematopoietic malignancy. In one patient with a pathogenic variant with a 50% VAF in the original skin culture, the variant was not present in a skin culture from a second, fresh skin biopsy done due to discordant phenotype. Conclusions Culturing of skin fibroblasts for germline genetic testing in patients with hematologic disorders has a high success rate, especially when cultures are initiated within 24 hours of collection, and adds on average 27 days to genetic testing turnaround time. From patients with a hereditary syndrome, most skin biopsies will culture with the exception of individuals with a short telomere syndrome. For this subset, a direct skin biopsy without culture may be necessary. Subclonal variants at VAFs relevant to interpretation of a germline test were found in 4% of cases. Half were confirmed in an alternative tissue. Etiology of the subclonal variants, whether acquired during the culturing process or due to mosaicism or sequencing biases was not always clear. Careful assessment of the clinical phenotype in interpreting and applying germline genetic results to patient care will always be warranted. Disclosures Godley: UptoDate, Inc.: Honoraria; Invitae, Inc.: Membership on an entity's Board of Directors or advisory committees. Segal:BMS: Consultancy, Research Funding; AbbVie: Consultancy; Merck: Consultancy; Astra Zeneca: Consultancy. Churpek:UpToDate, Inc: Honoraria.

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