Genome sequencing as a first-line diagnostic test for hospitalized infants.

PURPOSE: SouthSeq is a translational research study that undertook genome sequencing (GS) for infants with symptoms suggestive of a genetic disorder. Recruitment targeted racial/ethnic minorities and rural, medically underserved areas in the Southeastern United States, which are historically underrepresented in genomic medicine research. METHODS: GS and analysis were performed for 367 infants to detect disease-causal variation concurrent with standard of care evaluation and testing. RESULTS: Definitive diagnostic (DD) or likely diagnostic (LD) genetic findings were identified in 30% of infants, and 14% of infants harbored an uncertain result. Only 43% of DD/LD findings were identified via concurrent clinical genetic testing, suggesting that GS testing is better for obtaining early genetic diagnosis. We also identified phenotypes that correlate with the likelihood of receiving a DD/LD finding, such as craniofacial, ophthalmologic, auditory, skin, and hair abnormalities. We did not observe any differences in diagnostic rates between racial/ethnic groups. CONCLUSION: We describe one of the largest-to-date GS cohorts of ill infants, enriched for African American and rural patients. Our results show the utility of GS because it provides early-in-life detection of clinically relevant genetic variations not detected by current clinical genetic testing, particularly for infants exhibiting certain phenotypic features.

Mutations in origin recognition complex gene ORC4 cause Meier-Gorlin syndrome.

Meier-Gorlin syndrome is a rare autosomal recessive genetic condition whose primary clinical hallmarks include small stature, small external ears and small or absent patellae. Using marker-assisted mapping in multiple families from a founder population and traditional coding exon sequencing of positional candidate genes, we identified three different mutations in the gene encoding ORC4, a component of the eukaryotic origin recognition complex, in five individuals with Meier-Gorlin syndrome. In two such individuals that were negative for mutations in ORC4, we found potential mutations in ORC1 and CDT1, two other genes involved in origin recognition. ORC4 is well conserved in eukaryotes, and the yeast equivalent of the human ORC4 missense mutation was shown to be pathogenic in functional assays of cell growth. This is the first report, to our knowledge, of a germline mutation in any gene of the origin recognition complex in a vertebrate organism.

Ventricular fibrillation in a patient with Pompe disease: a cautionary tale.

Pompe disease is a rare genetic disorder resulting from a deficiency of the acid α-glucosidase enzyme. Although arrhythmias occur in these patients undergoing general anesthesia, they have not received sufficient emphasis in pediatric cardiology. We report a case of an infant with Pompe disease who experienced ventricular fibrillation during induction of anesthesia.

Mutations in UPF3B, a member of the nonsense-mediated mRNA decay complex, cause syndromic and nonsyndromic mental retardation.

Nonsense-mediated mRNA decay (NMD) is of universal biological significance. It has emerged as an important global RNA, DNA and translation regulatory pathway. By systematically sequencing 737 genes (annotated in the Vertebrate Genome Annotation database) on the human X chromosome in 250 families with X-linked mental retardation, we identified mutations in the UPF3 regulator of nonsense transcripts homolog B (yeast) (UPF3B) leading to protein truncations in three families: two with the Lujan-Fryns phenotype and one with the FG phenotype. We also identified a missense mutation in another family with nonsyndromic mental retardation. Three mutations lead to the introduction of a premature termination codon and subsequent NMD of mutant UPF3B mRNA. Protein blot analysis using lymphoblastoid cell lines from affected individuals showed an absence of the UPF3B protein in two families. The UPF3B protein is an important component of the NMD surveillance machinery. Our results directly implicate abnormalities of NMD in human disease and suggest at least partial redundancy of NMD pathways.

Initial experience with surgical treatment planning in the newly diagnosed breast cancer patient at high risk for BRCA-1 or BRCA-2 mutation.

Despite an abundance of information available for dealing with patients with BRCA-1 and BRCA-2 mutations, little guidance is available to assist the surgeon in dealing with the genetically high-risk patient recently diagnosed with breast cancer. A retrospective review was undertaken of 170 patients who underwent genetic counseling and testing over a 3-year period from March 2000 to March 2003. Forty-three of the 170 patients tested were diagnosed with breast cancer prior to genetic testing. Nine patients (20.9%) tested positive for a deleterious mutation. Fifty-eight percent underwent genetic counseling prior to definitive cancer surgery. Five of the 25 patients who underwent lumpectomy tested positive for a deleterious mutation. Testing results became available during systemic therapy or radiation was delayed until results were known. After counseling, all five patients testing positive went on to bilateral prophylactic mastectomy and reconstruction. None had radiation therapy. Because of a strong family history, eight patients elected to undergo prophylactic mastectomy and reconstruction prior to obtaining genetic test results; and despite compelling histories, all eight tested negative for a mutation. Treatment algorithms are developed to manage patients that are first discovered to be at high risk for a BRCA-1 or BRCA-2 mutation at the time they are diagnosed with breast cancer. Patients diagnosed with breast cancer who are discovered to be at high risk for a genetic mutation should undergo counseling prior to definitive surgery. This maximizes the time that patients have to consider options for prophylaxis and monitoring should their test be positive. It also prevents women who would otherwise be candidates for breast preservation from undergoing unnecessary radiation therapy should they chose prophylactic mastectomy in the face of a positive test.