Objective To identify the cause of childhood onset involuntary paroxysmal choreiform and dystonic movements in 2 unrelated sporadic cases and to investigate the functional effect of missense mutations in adenylyl cyclase 5 (ADCY5) in sporadic and inherited cases of autosomal dominant familial dyskinesia with facial myokymia (FDFM). Methods Whole exome sequencing was performed on 2 parent–child trios. The effect of mutations in ADCY5 was studied by measurement of cyclic adenosine monophosphate (cAMP) accumulation under stimulatory and inhibitory conditions. Results The same de novo mutation (c.1252C>T, p.R418W) in ADCY5 was found in both studied cases. An inherited missense mutation (c.2176G>A, p.A726T) in ADCY5 was previously reported in a family with FDFM. The significant phenotypic overlap with FDFM was recognized in both cases only after discovery of the molecular link. The inherited mutation in the FDFM family and the recurrent de novo mutation affect residues in different protein domains, the first cytoplasmic domain and the first membrane-spanning domain, respectively. Functional studies revealed a statistically significant increase in β-receptor agonist-stimulated intracellular cAMP consistent with an increase in adenylyl cyclase activity for both mutants relative to wild-type protein, indicative of a gain-of-function effect. Interpretation FDFM is likely caused by gain-of-function mutations in different domains of ADCY5—the first definitive link between adenylyl cyclase mutation and human disease. We have illustrated the power of hypothesis-free exome sequencing in establishing diagnoses in rare disorders with complex and variable phenotype. Mutations in ADCY5 should be considered in patients with undiagnosed complex movement disorders even in the absence of a family history.

Background: Familial dyskinesia with facial myokymia (FDFM) is an autosomal dominant disorder that is exacerbated by anxiety. In a 5-generation family of German ancestry, we previously mapped FDFM to chromosome band 3p21-3q21. The 72.5-Mb linkage region was too large for traditional positional mutation identification.Objective: To identify the gene responsible for FDFM by exome resequencing of a single affected individual.Participants: We performed whole exome sequencing in 1 affected individual and used a series of bioinformatic filters, including functional significance and presence in dbSNP or the 1000 Genomes Project, to reduce the number of candidate variants. Co-segregation analysis was performed in 15 additional individuals in 3 generations.Main Outcome Measures: Unique DNA variants in the linkage region that co-segregate with FDFM. Results:The exome contained 23 428 single-nucleotide variants, of which 9391 were missense, nonsense, or splice site alterations. The critical region contained 323 variants, 5 of which were not present in 1 of the sequence databases. Adenylyl cyclase 5 (ADCY5) was the only gene in which the variant (c.2176GϾA) was co-transmitted perfectly with disease status and was not present in 3510 control white exomes. This residue is highly conserved, and the change is nonconservative and predicted to be damaging.Conclusions: ADCY5 is highly expressed in striatum. Mice deficient in Adcy5 develop a movement disorder that is worsened by stress. We conclude that FDFM likely results from a missense mutation in ADCY5. This study demonstrates the power of a single exome sequence combined with linkage information to identify causative genes for rare autosomal dominant mendelian diseases.

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In order to clone candidate tumor suppressor genes whose loss contributes to the pathogenesis of neuroblastoma (NB), we performed polymerase chain reaction (PCR) screening using a high-density sequence tagged site-content map within a commonly deleted region (chromosome band 1p36) in 24 NB cell lines. We found a *480 kb homozygously deleted region at chromosome band 1p36.2 in one of the 24 NB cell lines, NB-1, and cloned the human homologue (KIF1B-b) of the mouseKif1B-b gene in this region. The KIF1B-b gene had at least 47 exons, all of which had a classic exon ± intron boundary structure. Mouse Kif1B is a microtubule-based putative anterograde motor protein for the transport of mitochondria in neural cells. We performed mutational analysis of the KIF1B-b gene in 23 cell lines using 46 sets of primers and also an allelic imbalance (AI) analysis of KIF1B-b in 50 fresh NB samples. A missense mutation at codon 1554, GTG (Gly) to ATG (Met), silent mutations at codon 409 (ACG to ACA) and codon 1721 (ACC to ACT), and polymorphisms at codon 170, GAT (Asp) to GAA (Glu), and at codon 1087, TAT (Tyr), to TGT (Cys), were all identi®ed, although their functional signi®cances remain to be determined. The AI for KIF1B-b was slightly higher (38%) than those for the other two markers (D1S244, D1S1350) (35 and 32%) within the commonly deleted region (1p36). Reverse transcriptase-PCR analysis of the KIF1B-b gene revealed obvious expression in all NB cell lines except NB-1, although decreased expression of the KIF1B-b gene was found in a subset of early-and advanced-stage NBs. These results suggest that the KIF1B-b gene may not be a candidate for tumor suppressor gene of NB. Oncogene (2001) 20, 5075 ± 5083.