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Functional Role of ?-Crystallin N in the Auditory Hindbrain.

ABSTRACT: ?-crystallins are major components of the vertebrate lens but show expression in other tissues as well. Their extralenticular functions remain so far unclear. Here, we explored such roles in the rodent superior olivary complex in which previous analysis demonstrated developmentally regulated expression of Crygd, Cryge and Crygn. Immunohistochemistry with novel antibodies against Crygd/e and Crygn indicate that expression of Crygd/e was moderate and varied between the perinatal superior olivary complex of mice, rats, and gerbils. Crygn-immunoreactivity was more robust and consistently highest in the medial nucleus of the trapezoid body, but also present in other nuclei of the superior olivary complex. To analyze the function of Crygn in the auditory hindbrain, we used a Crygn allele with a floxed exon 2. Upon pairing with Egr2::Cre mice, exon 2, encoding the first two greek key motifs of Crygn, was deleted in the developing auditory hindbrain. Anatomical analysis of these mice revealed a 20% volume reduction in the medial nucleus of the trapezoid body and a 7% reduction in the lateral superior olive at postnatal day 25. This was due to cell loss between postnatal days 4 and 25, whereas cell size was unaffected. Auditory brainstem responses showed normal threshold but a significant increase in the amplitude of wave IV. Crygn is hence required for postmigratory survival and proper function of auditory hindbrain neurons. These results ascertain for the first time an essential extralenticular role for ?-crystallins in vivo.

SUBMITTER: Hartwich H

PROVIDER: S-EPMC4982622 | biostudies-literature | 2016

REPOSITORIES: biostudies-literature

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Functional Role of γ-Crystallin N in the Auditory Hindbrain.

Hartwich Heiner H Rosengauer Elena E Rüttiger Lukas L Wilms Viviane V Waterholter Sarah-Kristin SK Nothwang Hans Gerd HG

PloS one 20160812 8

γ-crystallins are major components of the vertebrate lens but show expression in other tissues as well. Their extralenticular functions remain so far unclear. Here, we explored such roles in the rodent superior olivary complex in which previous analysis demonstrated developmentally regulated expression of Crygd, Cryge and Crygn. Immunohistochemistry with novel antibodies against Crygd/e and Crygn indicate that expression of Crygd/e was moderate and varied between the perinatal superior olivary c ...[more]

PMID: 27517863

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Project description:?-Crystallin is the major protein of the eye lens and a member of the family of small heat-shock proteins. Its concentration in the human eye lens is extremely high (about 450 mg/mL). Three-dimensional structure of native ?-crystallin is unknown. First of all, this is the result of the highly heterogeneous nature of ?-crystallin, which hampers obtaining it in a crystalline form. The modeling based on the electron microscopy (EM) analysis of ?-crystallin preparations shows that the main population of the ?-crystallin polydisperse complex is represented by oligomeric particles of rounded, slightly ellipsoidal shape with the diameter of about 13.5 nm. These complexes have molecular mass of about 700 kDa. In our opinion, the heterogeneity of the ?-crystallin complex makes it impossible to obtain a reliable 3D model. In the literature, there is evidence of an enhanced chaperone function of ?-crystallin during its dissociation into smaller components. This may indirectly indicate that the formation of heterogeneous complexes is probably necessary to preserve ?-crystallin in a state inactive before stressful conditions. Then, not only the heterogeneity of the ?-crystallin complex is an evolutionary adaptation that protects ?-crystallin from crystallization but also the enhancement of the function of ?-crystallin during its dissociation is also an evolutionary acquisition. An analysis of the literature on the study of ?-crystallin in vitro led us to the assumption that, of the two ?-crystallin isoforms (?A- and ?B-crystallins), it is ?A-crystallin that plays the role of a special chaperone for ?B-crystallin. In addition, our data on X-ray diffraction analysis of ?-crystallin at the sample concentration of about 170-190 mg/mL allowed us to assume that, at a high concentration, the eye lens ?-crystallin can be in a gel-like stage. Finally, we conclude that, since all the accumulated data on structural-functional studies of ?-crystallin were carried out under conditions far from native, they cannot adequately reflect the features of the functioning of ?-crystallin in vivo.

Project description:PURPOSE: To identify the underlying genetic defect in a north Indian family with seven members in three-generations affected with bilateral congenital cataract. METHODS: Detailed family history and clinical data were recorded. Linkage analysis using fluorescently labeled microsatellite markers for the already known candidate gene loci was performed in combination with mutation screening by bidirectional sequencing. RESULTS: Affected individuals had bilateral congenital cataract. Cataract was of opalescent type with the central nuclear region denser than the periphery. Linkage was excluded for the known cataract candidate gene loci at 1p34-36, 1q21-25 (gap junction protein, alpha 8 [GJA8]), 2q33-36 (crystallin, gamma A [CRYGA], crystallin, gamma B [CRYGB], crystallin, gamma C [CRYGC], crystallin, gamma D [CRYGD], crystallin, beta A2 [CRYBA2]), 3q21-22 (beaded filament structural protein 2, phakinin [BFSP2]), 12q12-14 (aquaporin 0 [AQP0]), 13q11-13 (gap junction protein, alpha 3 [GJA3]), 15q21-22, 16q22-23 (v-maf musculoaponeurotic fibrosarcoma oncogene homolog [MAF], heat shock transcription factor 4 [HSF4]), 17q11-12 (crystallin, beta A1 [CRYBA1]), 17q24, 21q22.3 (crystallin, alpha A [CRYAA]), and 22q11.2 (crystallin, beta B1 [CRYBB1], crystallin, beta B2 [CRYBB2], crystallin, beta B3 [CRYBB3], crystallin, beta A4 [CRYBA4]). Crystallin, alpha B (CRYAB) at chromosome 11q23-24 was excluded by sequence analysis. However, sequencing the candidate gene, crystallin, gamma S (CRYGS), at chromosome 3q26.3-qter showed a heterozygous c.176G-->A change that resulted in the replacement of a structurally highly conserved valine by methionine at codon 42 (p.V42M). This sequence change was not observed in unaffected family members or in the 100 ethnically matched controls. CONCLUSIONS: We report a novel missense mutation, p.V42M, in CRYGS associated with bilateral congenital cataract in a family of Indian origin. This is the third report of a mutation in this exceptional member of the beta-/gamma-crystallin superfamily and further substantiates the genetic and clinical heterogeneity of autosomal dominant cataract.

Dataset Information

Functional Role of ?-Crystallin N in the Auditory Hindbrain.

Publications

Functional Role of γ-Crystallin N in the Auditory Hindbrain.

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