Exome sequencing confirms the clinical diagnosis of both joubert syndrome and klinefelter syndrome with keratoconus in a han Chinese family.

Introduction: Joubert syndrome a rare genetic disorder, is characterized by abnormalities in the development of the central nervous system with "molar signs" on magnetic resonance imaging of the brain and accompanied by cerebellar vermis hypoplasia, ataxia, hypotonia, and developmental delay. Keratoconus (KC) is a kind of genetically predisposed eye disease that causes blindness characterized by a dilated thinning of the central or paracentral cornea conically projected forward, highly irregular astigmatism, and severe visual impairment. Klinefelter syndrome is caused by an extra X chromosome in the cells of male patients, and the main phenotype is tall stature and dysplasia with secondary sex characteristics. This study was intended to identify the genetic etiology and determine the clinical diagnosis of one Han Chinese family with specific clinical manifestations of keratoconus and multiorgan involvement. Methods: A comprehensive ocular and related general examination was performed on one patient and his asymptomatic parents and brother. Pathogenic genes were tested by exome sequencing. CNV-seq was used to verify the copy number variation, and peripheral blood was cultured for karyotype analysis. The pathogenicity of the identified variant was determined subject to ACMG guidelines. The Gene Expression Omnibus (GEO) dataset of keratoconus-related genes in the NCBI database was obtained to analyze the differentially expressed genes in corneal tissues of the keratoconus group and the normal control group, and analysis of protein-protein interaction networks (PPI) was performed. Results: Proband, a 25-year-old male, had sudden loss of vision in the left eye for 1 week. Best corrected visual acuity (BCVA): 0.5 (-1.00DS/-5.00DC*29°) in the right eye, counting fingers/40 cm in the left eye. Slit-lamp microscopy of the right eye showed mild anterior protrusion of the cornea and thinning of the cone-topped cornea. The left eye showed marked thinning of the central region of the cornea, rounded edema in the form of a cone-like bulge, epithelial bullae, edema and turbidity of the stroma, and bulging of the Descemet's membrane. Cranial magnetic resonance imaging (MRI) revealed changes in the midbrain and cerebellum, with a "molar sign" and a "bat-winged" ventriculus quartus cerebri. General check-up: 168 cm in height, decreased muscle tone in all four limbs, knee jerk elicited, negative Babinski sign, abdominal reflexes elicited, finger-to-nose test positive, intentional tremor evident in both hands, positive Romberg's sign, instability of gait, level I intellectual disability, poor adaptive behavior, communication disorders, teeth all dentures, a peculiar face with blepharophimosis, wide inner canthus distance, mild ptosis, severe positive epicanthus, high palatal arches, exotropia, hypotrichosis of beard and face, inconspicuous prominentia laryngea, and short upper and lower limbs. Exome sequencing detected compound heterozygous frameshift variants M1:c.9279dup:p.His3094Thrfs*18 and M2:c.6515_6522del:p.Lys2172Thrfs*37 in the patient's CPLANE1 gene and the presence of duplication-type CNV on the X chromosome. Sanger sequencing showed that the mother and father carried the M1 and M2 variants, respectively, and the younger brother carried the M2 variant, which was a novel variant. CNV-seq analysis showed the presence of a duplication-type CNV Xp22.33-Xq28 (2757837-156030895) of approximately 155 Mb on the X chromosome of the proband, which was a de novo variant and carried by neither of the parents. The two heterozygous frameshift variants and duplication-type CNV were pathogenic according to the ACMG guidelines. Differential expression analysis of keratoconus-related genes showed that CPLANE1 was upregulated in the corneal tissues of keratoconus patients compared with normal controls, and such a difference was statistically significant (p = 0.000515, <0.05). PPI analysis showed that the CPLANE1-NPHP3 complex protein acted as a bridge between cilia and extracellular matrix tissue. According to the genetic test results and clinical phenotype analysis, the family was finally diagnosed with Joubert syndrome combined with Keratoconus and Klinefelter syndrome. Discussion: In this study, we report a proband in a Han Chinese family with both Joubert syndrome and X-linked Klinefelter syndrome as well as keratoconus, and the phenotype spectrum of CPLANE1-Joubert syndrome may be expanded accordingly. Meanwhile, the significance of exome sequencing was emphasized in aiding the clinical diagnosis of complex cases, which is difficult to make.

Two novel PDE6C gene mutations in Chinese family with achromatopsia.

Background: Achromatopsia (ACHM) is an inherited retinal disease affecting the cone cell function. To date, six pathogenic genes of ACHM have been identified. However, the diagnostic and therapeutic methods of this disorder remain limited. Herein, to characterize the clinical features and genetic causes of three affected siblings in a Chinese family with ACHM, we used target next-generation sequencing (NGS) and found new pathogenic factors associated with ACHM in this family. Materials and methods: Three patients with ACHM and three healthy family members were included in this study. All participants received comprehensive ophthalmic tests. NGS approach was performed on the patients to determine the causative mutation for this family. The silico analysis was also applied to predict the pathogenesis of identified mutations. Results: Genetic assessments revealed compound heterozygous mutations of the PDE6C gene (c.1413 + 1 G > C, c.305 G > A), carried by all three patients. Both mutations were novel and predicted to be deleterious by six types of online predictive software. The heterozygous PDE6C missense mutation (c.305 G > A) was found from the mother and the heterozygous PDE6C splice site mutation (c.1413 + 1 G > C) was found in the father and all the children. All patients in the family showed typical signs and symptoms of ACHM. Conclusions: We report novel compound heterozygous PDE6C mutations in causing ACHM and further confirm the clinical diagnosis. Our study extends the genotypic spectrums for PDE6C-ACHM and better illustrates its genotype-phenotype correlations, which would help the ACHM patients with better genetic diagnosis, prognosis, and gene treatment.