NovelFGFR1 sequence variants in Kallmann syndrome, and genetic evidence that the FGFR1c isoform is required in olfactory bulb and palate morphogenesis
ABSTRACT In a new cohort of 141 unrelated patients affected by Kallmann syndrome we identified FGFR1 sequence variants in 17 patients, all in the heterozygous state. The fifteen novel variants consist of 10 missense (p.N77K, p.C101F, p.R250W, p.G270D, p.P283R, p.S332C, p.H621R, p.S685F, p.I693F, p.R822C), two nonsense (p.E324X, p.R661X), a frameshift (p.S439fs), and two splice site (c.1081G>C and c.1977+1G>A) changes. However, the p.N77K and p.R822C changes were also found in two and one out of 150 healthy control individuals, respectively, and therefore, their pathogenic effect is questionable. Notably, three alterations (p.E324X, p.S332C, c.1081G>C) are located in the alternative exon 8B that codes for the FGFR1c isoform, thus indicating that this isoform plays a crucial role in the development of the olfactory system in man. Moreover, the presence of cleft palate in a patient carrying the p.E324X change shows that FGFR1c is important for palate morphogenesis too.
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- "To date, hypogonadism associated with an olfactory deficit is defined as Kallmann syndrome (KS) and is distinct from normosmic HH (nHH), however both diseases share anatomical and genetic etiopathogenesis with common features. Many recent studies described several genes implicated in HH with different expressions also when the same mutation is present in different subjects within the same family (Pitteloud et al., 2006; Trarbach et al., 2006; Dodé et al., 2007), thus progressively thinning the border between KS and nHH. In fact, a recent study described mutations in genes previously thought to regulate primarily GnRH secretions in nHH (GNRHR, TAC3, KISS1, and KISS1R) in association with both normosmia and hyposmia; the precise mechanism is unclear but oligogenicity is a plausible reason (Lewkowitz-Shpuntoff et al., 2012). "
ABSTRACT: Introduction: Hypogonadotropic hypogonadism (HH) is a heterogeneous disease caused by mutations in several genes. Based on the presence of hyposmia/anosmia it is distinguished into Kallmann syndrome (KS) and isolated HH. The prevalence of other developmental anomalies is not well established. Methods: We studied 36 patients with HH (31 males, 5 females, mean age 41.5), 9 with familial and 27 with sporadic HH (33 congenital, 3 adult-onset), by physical examination, smell test (BSIT Sensonics), audiometry, renal ultrasound, and magnetic resonance imaging of the olfactory structures. Results: Based on the smell test, patients were classified as normosmic (n = 21, 58.3%) and hypo/anosmic (n = 15, 41.6%). Hypoplasia/agenesis of olfactory bulbs was found in 40% of patients (10/25; 75% hypo/anosmic, 7.6% normosmic, p < 0.01, Fisher’s test). Remarkably, olfactory structures were normal in two anosmic patients, while one normosmic patient presented a unilateral hypoplastic bulb. Fourteen of 33 patients (42.4%) presented neurosensorial hearing loss of various degrees (28.5% hypo/anosmic, 52.6% normosmic, p = NS). Renal ultrasound revealed 27.7% of cases with renal anomalies (26.6% hypo/anosmic, 28.5% normosmic, p = NS). At least one midline defect was found in 50% of the patients (53.3% hypo/anosmic, 47.6% normosmic, p = NS), including abnormal palate, dental anomalies, pectus excavatum, bimanual synkinesis, iris coloboma, and absent nasal cartilage. Anamnestically 4/31 patients reported cryptorchidism (25% hypo/anosmic, 5.2% normosmic, p = NS). Conclusion: Hypo/anosmia is significantly related to anatomical anomalies of the olfactory bulbs/tracts but the prevalence of other developmental anomalies, especially midline defects and neurosensorial hearing loss, is high both in HH and KS and independent of the presence of anosmia/hyposmia. From the clinical standpoint KS and normosmic HH should be considered as the same complex, developmental disease.Frontiers in Endocrinology 06/2013; 4:70. DOI:10.3389/fendo.2013.00070
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- "For the results we could infer that, I-Mutant 3.0 predict 68% deleterious nsSNPs, slightly higher than SIFT (37%), PolyPhen 2.0 (61%) and SNAP (58%). Most of the nsSNPs predicted to be deleterious were in very well concordance with the experimentally derived data, highlighting the accuracy of our prediction method (Trarbach et al., 2006; Albuisson et al., 2005; Greenman et al., 2007; Dode et al., 2003; Gerhard et al., 2004; Pitteloud et al., 2006; Muenke et al., 1994; Kress et al., 2009; White et al., 2005; Dode et al., 2007). "
ABSTRACT: Single amino acid substitutions in Fibroblast Growth Factor Receptor 1 (FGFR1) destabilize protein and have been implicated in several genetic disorders like various forms of cancer, Kallamann syndrome, Pfeiffer syn-drome, Jackson Weiss syndrome, etc. In order to gain functional insight into mutation caused by amino acid substitution to protein function and expression, special emphasis was laid on molecular dynamics simulation techniques in combination with in silico tools such as SIFT, PolyPhen 2.0, I-Mutant 3.0 and SNAP. It has been estimated that 68% nsSNPs were predicted to be deleterious by I-Mutant, slightly higher than SIFT (37%), PolyPhen 2.0 (61%) and SNAP (58%). From the observed results, P722S mutation was found to be most dele-terious by comparing results of all in silico tools. By molecular dynamics approach, we have shown that P722S mutation leads to increase in flexibility, and deviated more from the native structure which was supported by the decrease in the number of hydrogen bonds. In addition, biophysical analysis revealed a clear insight of stability loss due to P722S mutation in FGFR1 protein. Majority of mutations predicted by these in silico tools were in good concordance with the experimental results.Applied and Translational Genomics 06/2012; 1:37-43. DOI:10.1016/j.atg.2012.06.002
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- "The overlap between CHARGE and Kallmann syndromes was further explored by crossing Chd7Whi/+ mice with Fgfr1Hspy/+ mice. Fgfr1Hspy/+ mice have a missense mutation (W691R) in the conserved kinase domain of the Fgfr1 gene (one of the genes involved in Kallmann syndrome).12 This missense mutation causes a loss of receptor function (J Calvert, S Dedos, K Hawker and KP Steel, manuscript in preparation). "
ABSTRACT: CHARGE syndrome is a multiple congenital anomaly syndrome characterised by Coloboma, Heart defects, Atresia of choanae, Retardation of growth and/or development, Genital hypoplasia, and Ear anomalies often associated with deafness. It is caused by heterozygous mutations in the CHD7 gene and shows a highly variable phenotype. Anosmia and hypogonadotropic hypogonadism occur in the majority of the CHARGE patients, but the underlying pathogenesis is unknown. Therefore, we studied the ability to smell and aspects of the reproductive system (reproductive performance, gonadotropin-releasing hormone (GnRH) neurons and anatomy of testes and uteri) in a mouse model for CHARGE syndrome, the whirligig mouse (Chd7(Whi/+)). We showed that Chromodomain Helicase DNA-binding protein 7 (Chd7) is expressed in brain areas involved in olfaction and reproduction during embryonic development. We observed poorer performance in the smell test in adult Chd7(Whi/+) mice, secondary either to olfactory dysfunction or to balance disturbances. Olfactory bulb and reproductive organ abnormalities were observed in a proportion of Chd7(Whi/+) mice. Hypothalamic GnRH neurons were slightly reduced in Chd7(Whi/+) females and reproductive performance was slightly less in Chd7(Whi/+) mice. This study shows that the penetrance of anosmia and hypogonadotropic hypogonadism is lower in Chd7(Whi/+) mice than in CHARGE patients. Interestingly, many phenotypic features of the Chd7 mutation showed incomplete penetrance in our model mice, despite the use of inbred, genetically identical mice. This supports the theory that the extreme variability of the CHARGE phenotype in both humans and mice might be attributed to variations in the fetal microenvironment or to purely stochastic events.European journal of human genetics: EJHG 10/2009; 18(2):171-7. DOI:10.1038/ejhg.2009.158 · 4.35 Impact Factor