Next-generation sequencing of patients with congenital anosmia.

We performed whole exome or genome sequencing in eight multiply affected families with ostensibly isolated congenital anosmia. Hypothesis-free analyses based on the assumption of fully penetrant recessive/dominant/X-linked models obtained no strong single candidate variant in any of these families. In total, these eight families showed 548 rare segregating variants that were predicted to be damaging, in 510 genes. Three Kallmann syndrome genes (FGFR1, SEMA3A, and CHD7) were identified. We performed permutation-based analysis to test for overall enrichment of these 510 genes carrying these 548 variants with genes mutated in Kallmann syndrome and with a control set of genes mutated in hypogonadotrophic hypogonadism without anosmia. The variants were found to be enriched for Kallmann syndrome genes (3 observed vs. 0.398 expected, p = 0.007), but not for the second set of genes. Among these three variants, two have been already reported in genes related to syndromic anosmia (FGFR1 (p.(R250W)), CHD7 (p.(L2806V))) and one was novel (SEMA3A (p.(T717I))). To replicate these findings, we performed targeted sequencing of 16 genes involved in Kallmann syndrome and hypogonadotrophic hypogonadism in 29 additional families, mostly singletons. This yielded an additional 6 variants in 5 Kallmann syndrome genes (PROKR2, SEMA3A, CHD7, PROK2, ANOS1), two of them already reported to cause Kallmann syndrome. In all, our study suggests involvement of 6 syndromic Kallmann genes in isolated anosmia. Further, we report a yet unreported appearance of di-genic inheritance in a family with congenital isolated anosmia. These results are consistent with a complex molecular basis of congenital anosmia.

Mutations in olfactory signal transduction genes are not a major cause of human congenital general anosmia.

Anosmia affects the western world population, mostly the elderly, reaching to 5% in subjects over the age of 45 years and strongly lowering their quality of life. A smaller minority (about 0.01%) is born without a sense of smell, afflicted with congenital general anosmia (CGA). No causative genes for human CGA have been identified yet, except for some syndromic cases such as Kallman syndrome. In mice, however, deletion of any of the 3 main olfactory transduction components (guanidine triphosphate binding protein, adenylyl cyclase, and the cyclic adenosine monophosphate-gated channel) causes profound reduction of physiological responses to odorants. In an attempt to identify human CGA-related mutations, we performed whole-genome linkage analysis in affected families, but no significant linkage signals were observed, probably due to the small size of families analyzed. We further carried out direct mutation screening in the 3 main olfactory transduction genes in 64 unrelated anosmic individuals. No potentially causative mutations were identified, indicating that transduction gene variations underlie human CGA rarely and that mutations in other genes have to be identified. The screened genes were found to be under purifying selection, suggesting that they play a crucial functional role not only in olfaction but also potentially in additional pathways.

Nasal airflow and olfactory function after the repair of cleft palate (with and without cleft lip).

OBJECTIVE: The objective of this study was to examine nasal airflow and olfactory functions in patients with repaired cleft palate compared with matching normal controls. STUDY DESIGN: The all-cleft group consisted of 25 patients with hard palate cleft comprising 15 patients with unilateral cleft palate and lip (UCLP); 2 with CP but no cleft lip (UCLP subgroup) and 8 patients with bilateral cleft lip and palate (BCLP subgroup). All had had surgical correction of the palate in infancy. The control group consisted of 20 nonaffected orthodontic patients. The median age of both groups was 14 years. The tests included the following: (1) nasal airflow measured by anterior rhinomanometry, (2) smell threshold for isoamyl-acetate determined using a 3-way forced choice method, (3) a self-administered questionnaire regarding the subjective perception of smell sense function, and (4) orthonasal and retronasal smell identification (correct/incorrect) and hedonics using visual analog scale (VAS). RESULTS: The respective test results follow. (1) When compared with the control group, the total airflow in the UCLP subgroup was significantly lower especially on the affected side; while in the BCLP subgroup it was lower than in the control group bilaterally. No significant difference was found between the cleft side of UCLP and BCLP subgroups. (2) The smell threshold of the UCLP subgroup was significantly higher than that of the control group and BCLP subgroup. No significant differences were found between right and left nostrils within the BCLP patients and between them and the control group. (3) No difference was found between the groups regarding the subjective perception of smell. (4) No significant differences were found between the UCLP and BCLP subgroups and between the all-cleft group and the control group, except for one item, regarding orthonasal and retronasal smell identification and hedonics. CONCLUSION: Although nasal airflow is significantly lower and the smell threshold higher on the cleft side, the day-to-day function of the sense of smell of cleft patients is similar to that of normal controls.