Implementation of genomic medicine for rare disease in a tertiary healthcare system: Mayo Clinic Program for Rare and Undiagnosed Diseases (PRaUD)

BACKGROUND

In the United States, rare disease (RD) is defined as a condition that affects fewer than 200,000 individuals. Collectively, RD affects an estimated 30 million Americans. A significant portion of RD has an underlying genetic cause; however, this may go undiagnosed. To better serve these patients, the Mayo Clinic Program for Rare and Undiagnosed Diseases (PRaUD) was created under the auspices of the Center for Individualized Medicine (CIM) aiming to integrate genomics into subspecialty practice including targeted genetic testing, research, and education.

METHODS

Patients were identified by subspecialty healthcare providers from 11 clinical divisions/departments. Targeted multi-gene panels or custom exome/genome-based panels were utilized. To support the goals of PRaUD, a new clinical service model, the Genetic Testing and Counseling (GTAC) unit, was established to improve access and increase efficiency for genetic test facilitation. The GTAC unit includes genetic counselors, genetic counseling assistants, genetic nurses, and a medical geneticist. Patients receive abbreviated point-of-care genetic counseling and testing through a partnership with subspecialty providers.

RESULTS

Implementation of PRaUD began in 2018 and GTAC unit launched in 2020 to support program expansion. Currently, 29 RD clinical indications are included in 11 specialty divisions/departments with over 142 referring providers. To date, 1152 patients have been evaluated with an overall solved or likely solved rate of 17.5% and as high as 66.7% depending on the phenotype. Noteworthy, 42.7% of the solved or likely solved patients underwent changes in medical management and outcome based on genetic test results.

CONCLUSION

Implementation of PRaUD and GTAC have enabled subspecialty practices advance expertise in RD where genetic counselors have not historically been embedded in practice. Democratizing access to genetic testing and counseling can broaden the reach of patients with RD and increase the diagnostic yield of such indications leading to better medical management as well as expanding research opportunities.

Risk of Syndrome-Associated Cancers Among First-Degree Relatives of Patients With Pancreatic Ductal Adenocarcinoma With Pathogenic or Likely Pathogenic Germline Variants

Importance

Increased cancer risk in first-degree relatives of probands with pancreatic ductal adenocarcinoma (PDAC probands) who carry pathogenic or likely pathogenic germline variants (PGVs) in cancer syndrome-associated genes encourages cascade genetic testing. To date, unbiased risk estimates for the development of cancers on a gene-specific basis have not been assessed.

Objective

To quantify the risk of development of PDAC and extra-PDAC among first-degree relatives of PDAC probands who carry a PGV in 1 of 9 cancer syndrome-associated genes-ATM, BRCA1, BRCA2, PALB2, MLH1, MSH2, MSH6, PMS2, and CDKN2A.

Design, Setting, and Participants

This case series focused on first-degree relatives of PDAC probands carrying PGVs in specific cancer syndrome-associated genes. The cohort comprised clinic-ascertained patients enrolled in the Mayo Clinic Biospecimen Resource for Pancreas Research registry with germline genetic testing. In total, 234 PDAC probands carrying PGVs were drawn from the prospective research registry of 4562 participants who had undergone genetic testing of cancer syndrome-associated genes. Demographic and cancer-related family histories were obtained by questionnaire. The data were collected from October 1, 2000, to December 31, 2021.

Main Outcomes and Measures

For the PDAC probands, the genetic test results of the presence of PGVs in 9 cancer syndrome-associated genes were obtained by clinical testing. Cancers (ovary, breast, uterus or endometrial, colon, malignant melanoma, and pancreas) among first-degree relatives were reported by the probands. Standardized incidence ratios (SIRs) were used to estimate cancer risks among first-degree relatives of PDAC probands carrying a PGV.

Results

In total, 1670 first-degree relatives (mean [SD] age, 58.1 [17.8] years; 853 male [51.1%]) of 234 PDAC probands (mean [SD] age, 62.5 [10.1] years; 124 male [53.0%]; 219 [94.4%] White; 225 [98.7%] non-Hispanic or non-Latino]) were included in the study. There was a significantly increased risk of ovarian cancer in female first-degree relatives of probands who had variants in BRCA1 (SIR, 9.49; 95% CI, 3.06-22.14) and BRCA2 (SIR, 3.72; 95% CI, 1.36-8.11). Breast cancer risks were higher with BRCA2 variants (SIR, 2.62; 95% CI, 1.89-3.54). The risks of uterine or endometrial cancer (SIR, 6.53; 95% CI, 2.81-12.86) and colon cancer (SIR, 5.83; 95% CI, 3.70-8.75) were increased in first-degree relatives of probands who carried Lynch syndrome mismatch repair variants. Risk of PDAC was also increased for variants in ATM (SIR, 4.53; 95% CI, 2.69-7.16), BRCA2 (SIR, 3.45; 95% CI, 1.72-6.17), CDKN2A (SIR, 7.38; 95% CI, 3.18-14.54), and PALB2 (SIR, 5.39; 95% CI, 1.45-13.79). Melanoma risk was elevated for first-degree relatives of probands with CDKN2A variants (SIR, 7.47; 95% CI, 3.97-12.77).

Conclusions and Relevance

In this case series, the presence of PGVs in 9 cancer syndrome-associated genes in PDAC probands was found to be associated with increased risk of 6 types of cancers in first-degree relatives. These gene-specific PDAC and extra-PDAC cancer risks may provide justification for clinicians to counsel first-degree relatives about the relevance and importance of genetic cascade testing, with the goal of higher uptake of testing.

De novo coding variants in the AGO1 gene cause a neurodevelopmental disorder with intellectual disability

BACKGROUND

High-impact pathogenic variants in more than a thousand genes are involved in Mendelian forms of neurodevelopmental disorders (NDD).

METHODS

This study describes the molecular and clinical characterisation of 28 probands with NDD harbouring heterozygous AGO1 coding variants, occurring de novo for all those whose transmission could have been verified (26/28).

RESULTS

A total of 15 unique variants leading to amino acid changes or deletions were identified: 12 missense variants, two in-frame deletions of one codon, and one canonical splice variant leading to a deletion of two amino acid residues. Recurrently identified variants were present in several unrelated individuals: p.(Phe180del), p.(Leu190Pro), p.(Leu190Arg), p.(Gly199Ser), p.(Val254Ile) and p.(Glu376del). AGO1 encodes the Argonaute 1 protein, which functions in gene-silencing pathways mediated by small non-coding RNAs. Three-dimensional protein structure predictions suggest that these variants might alter the flexibility of the AGO1 linker domains, which likely would impair its function in mRNA processing. Affected individuals present with intellectual disability of varying severity, as well as speech and motor delay, autistic behaviour and additional behavioural manifestations.

CONCLUSION

Our study establishes that de novo coding variants in AGO1 are involved in a novel monogenic form of NDD, highly similar to the recently reported AGO2-related NDD.

Pancreatic cancer risk to siblings of probands in bilineal cancer settings

PURPOSE

Pancreatic cancer (PC) risk is increased in families, but PC risk and risk perception have been understudied when both parents have cancer.

METHODS

An unbiased method defining cancer triads (proband with PC and both parents with cancer) in a prospective registry estimated risk of PC to probands' siblings in triad group 1 (no parent with PC), group 2 (1 parent with PC), and group 3 (both parents with PC). We estimated standardized incidence ratios (SIRs) using a Surveillance, Epidemiology, and End Results (SEER) reference. We also estimated the risk when triad probands carried germline pathogenic/likely pathogenic variants in any of the 6 PC-associated genes (ATM, BRCA1, BRCA2, CDKN2A, MLH1, and TP53). PC risk perception/concern was surveyed in siblings and controls.

RESULTS

Risk of PC was higher (SIR = 3.5; 95% CI = 2.2-5.2) in 933 at-risk siblings from 297 triads. Risk increased by triad group: 2.8 (95% CI = 1.5-4.5); 4.5 (95% CI = 1.6-9.7); and 21.2 (95% CI = 4.3-62.0). SIR in variant-negative triads was 3.0 (95% CI = 1.6-5.0), whereas SIR in variant-positive triads was 10.0 (95% CI = 3.2-23.4). Siblings' perceived risk/concern of developing PC increased by triad group.

CONCLUSION

Sibling risks were 2.8- to 21.2-fold higher than that of the general population. Positive variant status increased the risk in triads. Increasing number of PC cases in a triad was associated with increased concern and perceived PC risk.

Genomics Integration Into Nephrology Practice

RATIONALE & OBJECTIVE

The etiology of kidney disease remains unknown in many individuals with chronic kidney disease (CKD). We created the Mayo Clinic Nephrology Genomics Clinic to improve our ability to integrate genomic and clinical data to identify the etiology of unexplained CKD.

STUDY DESIGN

Retrospective study.

SETTING & PARTICIPANTS

An essential component of our program is the Nephrology Genomics Board which consists of nephrologists, geneticists, pathologists, translational omics scientists, and trainees who interpret the patient's clinical and genetic data. Since September 2016, the Board has reviewed 163 cases (15 cystic, 100 glomerular, 6 congenital anomalies of kidney and urinary tract (CAKUT), 20 stones, 15 tubulointerstitial, and 13 other).

ANALYTICAL APPROACH

Testing was performed with targeted panels, single gene analysis, or analysis of kidney-related genes from exome sequencing. Variant classification was obtained based on the 2015 American College of Medical Genetics and Genomics and the Association for Molecular Pathology guidelines.

RESULTS

A definitive genetic diagnosis was achieved for 50 families (30.7%). The highest diagnostic yield was obtained in individuals with tubulointerstitial diseases (53.3%), followed by congenital anomalies of the kidney and urological tract (33.3%), glomerular (31%), cysts (26.7%), stones (25%), and others (15.4%). A further 20 (12.3%) patients had variants of interest, and variant segregation, and research activities (exome, genome, or transcriptome sequencing) are ongoing for 44 (40%) unresolved families.

LIMITATIONS

Possible overestimation of diagnostic rate due to inclusion of individuals with variants with evidence of pathogenicity but classified as of uncertain significance by the clinical laboratory.

CONCLUSIONS

Integration of genomic and research testing and multidisciplinary evaluation in a nephrology cohort with CKD of unknown etiology or suspected monogenic disease provided a diagnosis in a third of families. These diagnoses had prognostic implications, and often changes in management were implemented.

Impact of integrated translational research on clinical exome sequencing

PURPOSE

Exome sequencing often identifies pathogenic genetic variants in patients with undiagnosed diseases. Nevertheless, frequent findings of variants of uncertain significance necessitate additional efforts to establish causality before reaching a conclusive diagnosis. To provide comprehensive genomic testing to patients with undiagnosed disease, we established an Individualized Medicine Clinic, which offered clinical exome testing and included a Translational Omics Program (TOP) that provided variant curation, research activities, or research exome sequencing.

METHODS

From 2012 to 2018, 1101 unselected patients with undiagnosed diseases received exome testing. Outcomes were reviewed to assess impact of the TOP and patient characteristics on diagnostic rates through descriptive and multivariate analyses.

RESULTS

The overall diagnostic yield was 24.9% (274 of 1101 patients), with 174 (15.8% of 1101) diagnosed on the basis of clinical exome sequencing alone. Four hundred twenty-three patients with nondiagnostic or without access to clinical exome sequencing were evaluated by the TOP, with 100 (9% of 1101) patients receiving a diagnosis, accounting for 36.5% of the diagnostic yield. The identification of a genetic diagnosis was influenced by the age at time of testing and the disease phenotype of the patient.

CONCLUSION

Integration of translational research activities into clinical practice of a tertiary medical center can significantly increase the diagnostic yield of patients with undiagnosed disease.

Safety and efficacy of (+)-epicatechin in subjects with Friedreich's ataxia: A phase II, open-label, prospective study

BACKGROUND

(+)-Epicatechin (EPI) induces mitochondrial biogenesis and antioxidant metabolism in muscle fibers and neurons. We aimed to evaluate safety and efficacy of (+)-EPI in pediatric subjects with Friedreich's ataxia (FRDA).

METHODS

This was a phase II, open-label, baseline-controlled single-center trial including 10 participants ages 10 to 22 with confirmed FA diagnosis. (+)-EPI was administered orally at 75 mg/d for 24 weeks, with escalation to 150 mg/d at 12 weeks for subjects not showing improvement of neuromuscular, neurological or cardiac endpoints. Neurological endpoints were change from baseline in Friedreich's Ataxia Rating Scale (FARS) and 8-m timed walk. Cardiac endpoints were changes from baseline in left ventricular (LV) structure and function by cardiac magnetic resonance imaging (MRI) and echocardiogram, changes in cardiac electrophysiology, and changes in biomarkers for heart failure and hypertrophy.

RESULTS

Mean FARS/modified (m)FARS scores showed nonstatistically significant improvement by both group and individual analysis. FARS/mFARS scores improved in 5/9 subjects (56%), 8-m walk in 3/9 (33%), 9-peg hole test in 6/10 (60%). LV mass index by cardiac MRI was significantly reduced at 12 weeks (P = .045), and was improved in 7/10 (70%) subjects at 24 weeks. Mean LV ejection fraction was increased at 24 weeks (P = .008) compared to baseline. Mean maximal septal thickness by echocardiography was increased at 24 weeks (P = .031). There were no serious adverse events.

CONCLUSION

(+)-EPI was well tolerated over 24 weeks at up to 150 mg/d. Improvement was observed in cardiac structure and function in subset of subjects with FRDA without statistically significant improvement in primary neurological outcomes.

SYNOPSIS

A (+)-epicatechin showed improvement of cardiac function, nonsignificant reduction of FARS/mFARS scores, and sustained significant upregulation of muscle-regeneration biomarker follistatin.

Three rare disease diagnoses in one patient through exome sequencing

Diagnostic exome sequencing yields a single genetic diagnosis in ∼30% of cases, and according to recent studies the prevalence of identifying two genetic conditions in a single individual range between 4.6% and 7%. We present a patient diagnosed with three different rare conditions, each explained by a pathogenic variant in a different gene. A 17-yr-old female was evaluated for a history of motor and speech delay, scoliosis, distinctive craniofacial features, and dry skin in the Department of Clinical Genomics at Mayo Clinic. Her distinctive features included prominent forehead, epicanthus, depressed nasal bridge, narrow mouth, prognathism, malar flattening, and oligodontia. Family history was notable for dry skin in her mother and missing teeth in the paternal grandmother. Previous diagnostic testing was unrevealing including biochemical testing, echocardiogram, abdominal ultrasound, and electroencephalogram. Previous genetic testing included a microarray-based comparative genomic hybridization that was reported normal. Three pathogenic loss-of-function heterozygous variants were identified by exome trio sequencing, each linked to different genetic conditions: SIN3A (Witteveen–Kolk syndrome), FLG (dermatitis), and EDAR (ectodermal dysplasia). Together, these three genetic alterations could explain the patient's overall phenotype. This patient demonstrates the importance of performing a thorough curation of exome data when presented with a complex phenotype. Although phenotypic variability can explain some of these situations, the hypothesis of multiple diseases coexisting in a single patient should never be disregarded completely.

Phenotypic Variability of c.436delC DCAF17 Gene Mutation in Woodhouse-Sakati Syndrome

Case series

Patients: 38, female • 28, female • 41, female • 18, female • 23, male

Final Diagnosis: Woodhouse-Sakati syndrome

Symptoms: Hypogonadism • dystonia • alopecia • hearing loss • diabetes

Medication: —

Clinical Procedure: —

Specialty: Endocrinology and Metabolic

A Novel Kleefstra Syndrome-associated Variant That Affects the Conserved TPLX Motif within the Ankyrin Repeat of EHMT1 Leads to Abnormal Protein Folding

Kleefstra syndrome (KS) (Mendelian Inheritance in Man (MIM) no. 610253), also known as 9q34 deletion syndrome, is an autosomal dominant disorder caused by haploinsufficiency of euchromatic histone methyltransferase-1 (EHMT1). The clinical phenotype of KS includes moderate to severe intellectual disability with absent speech, hypotonia, brachycephaly, congenital heart defects, and dysmorphic facial features with hypertelorism, synophrys, macroglossia, protruding tongue, and prognathism. Only a few cases of de novo missense mutations in EHMT1 giving rise to KS have been described. However, some EHMT1 variants have been described in individuals presenting with autism spectrum disorder or mild intellectual disability, suggesting that the phenotypic spectrum resulting from EHMT1 alterations may be quite broad. In this report, we describe two unrelated patients with complex medical histories consistent with KS in whom next generation sequencing identified the same novel c.2426C>T (p.P809L) missense variant in EHMT1. To examine the functional significance of this novel variant, we performed molecular dynamics simulations of the wild type and p.P809L variant, which predicted that the latter would have a propensity to misfold, leading to abnormal histone mark binding. Recombinant EHMT1 p.P809L was also studied using far UV circular dichroism spectroscopy and intrinsic protein fluorescence. These functional studies confirmed the model-based hypotheses and provided evidence for protein misfolding and aberrant target recognition as the underlying pathogenic mechanism for this novel KS-associated variant. This is the first report to suggest that missense variants in EHMT1 that lead to protein misfolding and disrupted histone mark binding can lead to KS.