Sumito Dateki

OTX2 Mutation in a Patient with Anophthalmia, Short Stature, and Partial Growth Hormone Deficiency: Functional Studies Using the IRBP, HESX1, and POU1F1 Promoters

CONTEXT OTX2 is a transcription factor gene essential for eye development. Although recent studies suggest the involvement of OTX2 in pituitary function, there is no report demonstrating a positive role of OTX2 in the pituitary function. OBJECTIVE The objective of the study was to report the results of functional studies indicating the relevance of OTX2 to pituitary function. PATIENT A Japanese female patient with bilateral anophthalmia was found to have short stature (height, -3.3 sd) and isolated partial GH deficiency (peak serum GH 3.1 and 9.7 mug/liter after insulin and arginine stimulations, respectively; serum IGF-I 37 ng/ml) at 3 yr 9 months of age. Magnetic resonance imaging delineated apparently normal pituitary gland. RESULTS Mutation analysis showed a de novo heterozygous frameshift mutation (c.402insC) that is predicted to retain the homeodomain but lose the transactivation domain. Functional studies revealed that the wild-type and mutant OTX2 proteins localized to the nucleus and bound to the target sequences within the IRBP (interstitial retinoid-binding protein), HESX1 (HESX homeobox 1), and POU1F1 promoters. Furthermore, the wild-type OTX2 protein markedly transactivated the promoters of IRBP ( approximately 27-fold), HESX1 ( approximately 4.5-fold), and POU1F1 ( approximately 19-fold), whereas the mutant OTX2 protein barely retained the transactivation activities and had no dominant-negative effects. CONCLUSIONS The results provide direct evidence for OTX2 being involved in the pituitary function. It is likely that the heterozygous severe OTX2 loss-of-function mutation caused GH deficiency and short stature, primarily because of decreased transactivation function for HESX1 and POU1F1.

Mutation and Gene Copy Number Analyses of Six Pituitary Transcription Factor Genes in 71 Patients with Combined Pituitary Hormone Deficiency: Identification of a Single Patient with LHX4 Deletion

CONTEXT Mutations of multiple transcription factor genes involved in pituitary development have been identified in a minor portion of patients with combined pituitary hormone deficiency (CPHD). However, copy number aberrations involving such genes have been poorly investigated in patients with CPHD. OBJECTIVE We aimed to report the results of mutation and gene copy number analyses in patients with CPHD. SUBJECTS AND METHODS Seventy-one Japanese patients with CPHD were examined for mutations and gene copy number aberrations affecting POU1F1, PROP1, HESX1, LHX3, LHX4, and SOX3 by PCR-direct sequencing and multiplex ligation-dependent probe amplification. When a deletion was indicated, it was further studied by fluorescence in situ hybridization, oligoarray comparative genomic hybridization, and serial sequencing for long PCR products encompassing the deletion junction. RESULTS We identified a de novo heterozygous 522,009-bp deletion involving LHX4 in a patient with CPHD (GH, TSH, PRL, LH, and FSH deficiencies), anterior pituitary hypoplasia, ectopic posterior pituitary, and underdeveloped sella turcica. We also identified five novel heterozygous missense substitutions (p.V201I and p.H387P in LHX4, p.T63M and p.A322T in LHX3, and p.V53L in SOX3) that were assessed as rare variants by sequencing analyses for control subjects and available parents and by functional studies and in silico analyses. CONCLUSIONS The results imply the rarity of abnormalities affecting the six genes in patients with CPHD and the significance of the gene copy number analysis in such patients.

A novel loss-of-function mutation in OTX2 in a patient with anophthalmia and isolated growth hormone deficiency

Heterozygous mutations of the gene encoding transcription factor OTX2 were recently shown to be responsible for ocular as well as pituitary abnormalities. Here, we describe a patient with unilateral anophthalmia and short stature. Endocrine evaluation of the hypothalamic–pituitary axis revealed isolated growth hormone deficiency (IGHD) with small anterior pituitary gland, invisible stalk, ectopic posterior lobe, and right anophthalmia on brain magnetic resonance imaging. DNA was analyzed for mutations in the HESX1, SOX2, and OTX2 genes. Molecular analysis yielded a novel heterozygous OTX2 mutation (c.270A>T, p.R90S) within the homeodomain. Functional analysis revealed that the mutation inhibited both the DNA binding and transactivation activities of the protein. This novel loss-of-function mutation is associated with anophthalmia and IGHD in a patient of Sephardic Jewish descent. We recommend that patients with GH deficiency and ocular malformation in whom genetic analysis for classic transcription factor genes (PROP1, POU1F1, HESX1, and LHX4) failed to identify alterations should be checked for the presence of mutations in the OTX2 gene.

SLC25A13 Gene Analysis in Citrin Deficiency: Sixteen Novel Mutations in East Asian Patients, and the Mutation Distribution in a Large Pediatric Cohort in China

Background The human SLC25A13 gene encodes citrin, the liver-type mitochondrial aspartate/glutamate carrier isoform 2 (AGC2), and SLC25A13 mutations cause citrin deficiency (CD), a disease entity that encompasses different age-dependant clinical phenotypes such as Adult-onset Citrullinemia Type II (CTLN2) and Neonatal Intrahepatic Cholestasis caused by Citrin Deficiency (NICCD). The analyses of SLC25A13 gene and its protein/mRNA products remain reliable tools for the definitive diagnoses of CD patients, and so far, the SLC25A13 mutation spectrum in Chinese CD patients has not been well-characterized yet. Methods and Results By means of direct DNA sequencing, cDNA cloning and SNP analyses, 16 novel pathogenic mutations, including 9 missense, 4 nonsense, 1 splice-site, 1 deletion and 1 large transposal insertion IVS4ins6kb (GenBank accession number KF425758), were identified in CTLN2 or NICCD patients from China, Japan and Malaysia, respectively, making the SLC25A13 variations worldwide reach the total number of 81. A large NICCD cohort of 116 Chinese cases was also established, and the 4 high-frequency mutations contributed a much larger proportion of the mutated alleles in the patients from south China than in those from the north (χ2 = 14.93, P<0.01), with the latitude of 30°N as the geographic dividing line in mainland China. Conclusions This paper further enriched the SLC25A13 variation spectrum worldwide, and formed a substantial contribution to the in-depth understanding of the genotypic feature of Chinese CD patients.

Hypothalamic Dysfunction in a Female with Isolated Hypogonadotropic Hypogonadism and Compound Heterozygous TACR3 Mutations and Clinical Manifestation in Her Heterozygous Mother

Background/Aims:TAC3 and TACR3 have recently been shown to be causative genes for an autosomal recessive form of isolated hypogonadotropic hypogonadism (IHH). Here, we report a Japanese female with IHH and compound heterozygous TACR3 mutations and her heterozygous parents, and discuss the primary lesion for IHH and clinical findings. Case Report: This female was identified through mutation analysis of TAC3 and TACR3 in 57 patients with IHH. At 24 years of age, an initial standard GnRH test showed poor gonadotropin response (LH <0.2–0.6 IU/l), whereas the second GnRH test performed after GnRH priming (100 µg i.m. for 5 consecutive days) revealed ameliorated gonadotropin responses (LH 0.3–6.4 IU/l; FSH 2.2–9.6 IU/l). The mother exhibited several features suggestive of mild IHH, whereas the father showed an apparently normal phenotype. Results: She had a paternally derived nonsense mutation at exon 1 (Y145X) and a maternally inherited single nucleotide (G) deletion from the conserved ‘GT’ splice donor site of intron 1 (IVS1+1delG). Conclusions: The results suggest hypothalamic dysfunction as the primary cause for IHH in patients with biallelic TACR3 mutations and clinical manifestation in heterozygous females, together with the rarity of TAC3 and TACR3 mutations in patients with IHH.

Identification and characterization of cryptic SHOX intragenic deletions in three Japanese patients with Léri–Weill dyschondrosteosis

AbstractAlthough short-stature homeobox-containing gene (SHOX ) haploinsufficiency is responsible for Léri–Weill dyschondrosteosis (LWD), the molecular defect has not been identified in ∼20% of Japanese LWD patients. Furthermore, although high prevalence of microdeletions affecting SHOX is primarily ascribed to the presence of repeat sequences such as Alu elements around SHOX, it remains to be determined whether microdeletions are actually mediated by repeat sequences. We performed multiple ligation probe amplification (MLPA) assay in six Japanese LWD patients with apparently normal SHOX, followed by fluorescent in situ hybridization (FISH) analysis and sequencing for polymerase chain reaction (PCR) products encompassing the deletion junctions in patients with abnormal MLPA patterns. Consequently, heterozygous intragenic deletions were identified in three cases, i.e., a 5,906-bp deletion involving exons 4–5 in case 1, a 5,594-bp deletion involving exons 4–6a in case 2, and a 50,199-bp deletion involving exons 4–6b in case 3. The deletion breakpoints of cases 1 and 2 were present in nonrepeat sequences, whereas those of case 3 resided within Alu elements. The results suggest that cryptic SHOX intragenic deletions account for a small fraction of LWD and that microdeletions affecting SHOX can be generated by repeat-sequence-mediated aberrant recombinations and by nonhomologous end joining.

Rare pseudoautosomal copy-number variations involving SHOX and/or its flanking regions in individuals with and without short stature

Pseudoautosomal region 1 (PAR1) contains SHOX, in addition to seven highly conserved non-coding DNA elements (CNEs) with cis-regulatory activity. Microdeletions involving SHOX exons 1–6a and/or the CNEs result in idiopathic short stature (ISS) and Leri–Weill dyschondrosteosis (LWD). Here, we report six rare copy-number variations (CNVs) in PAR1 identified through copy-number analyzes of 245 ISS/LWD patients and 15 unaffected individuals. The six CNVs consisted of three microduplications encompassing SHOX and some of the CNEs, two microduplications in the SHOX 3′-region affecting one or four of the downstream CNEs, and a microdeletion involving SHOX exon 6b and its neighboring CNE. The amplified DNA fragments of two SHOX-containing duplications were detected at chromosomal regions adjacent to the original positions. The breakpoints of a SHOX-containing duplication resided within Alu repeats. A microduplication encompassing four downstream CNEs was identified in an unaffected father–daughter pair, whereas the other five CNVs were detected in ISS patients. These results suggest that microduplications involving SHOX cause ISS by disrupting the cis-regulatory machinery of this gene and that at least some of microduplications in PAR1 arise from Alu-mediated non-allelic homologous recombination. The pathogenicity of other rare PAR1-linked CNVs, such as CNE-containing microduplications and exon 6b-flanking microdeletions, merits further investigation.

Identification of a novel heterozygous mutation of the Aggrecan gene in a family with idiopathic short stature and multiple intervertebral disc herniation

Aggrecan is a critical proteoglycan component of the extracellular matrix of the growth plates and articular cartilage and has a key role in the biophysical and biomechanical properties of cartilage. Recently, heterozygous mutations in the ACAN gene, which encodes aggrecan, have been identified in patients with short stature and accelerated bone age. We herein report another family with a heterozygous ACAN mutation associated with idiopathic short stature along with accelerated bone age and early-onset herniation of the lumbar discs at the levels of L1/2 through L5/S1. Whole-exome sequencing identified a novel heterozygous frameshift mutation in the ACAN gene (c.1744delT; p.Phe582fs*69) in all of the affected family members but not in the unaffected one, providing further evidence that ACAN haploinsufficiency causes short stature with advanced bone maturation. In addition, we advocate early-onset multiple disc herniation as a novel phenotype associated with ACAN haploinsufficiency.

Systematic molecular analyses of SHOX in Japanese patients with idiopathic short stature and Leri-Weill dyschondrosteosis

The etiology of idiopathic short stature (ISS) and Leri–Weill dyschondrosteosis (LWD) in European patients is known to include SHOX mutations and copy-number variations (CNVs) involving SHOX and/or the highly evolutionarily conserved non-coding DNA elements (CNEs) flanking the gene. However, the frequency and types of SHOX abnormalities in non-European patients and the clinical importance of mutations in the CNEs remains to be clarified. Here, we performed systematic molecular analyses of SHOX for 328 Japanese patients with ISS or LWD. SHOX abnormalities accounted for 3.8% of ISS and 50% of LWD cases. CNVs around SHOX were identified in 16 cases, although the ~47 kb deletion frequently reported in European patients was absent in our cases. Probably damaging mutations and benign/silent substitutions were detected in four cases, respectively. Although CNE-linked substitutions were detected in 15 cases, most of them affected poorly conserved nucleotides and were shared by unaffected individuals. These results suggest that the frequency and mutation spectrum of SHOX abnormalities are comparable between Asian and European patients, with the exception of a European-specific downstream deletion. Furthermore, this study highlights the clinical importance and genetic heterogeneity of the SHOX-flanking CNVs, and indicates a limited clinical significance of point mutations in the CNEs.

A Japanese patient with a mild Lenz–Majewski syndrome

AbstractWe report on a sclerosing bone dysplasia, associated with cutis laxa, enamel dysplasia, and mental retardation. The patient was a 17-year-old Japanese boy of normal height and muscular build. Cutis laxa with prominent veins in the scalp and abdominal wall and delayed eruption of permanent teeth attracted the attention of clinicians in infancy and adolescence, respectively. The clinical manifestations included a progeroid facial appearance with prognathism, wrinkled skin, and interdigital webbing. The intelligence quotient was estimated at 60. Enamel dysplasia was histologically confirmed. Skeletal changes included calvarial hyperostosis, sclerosis of the skull base, an enlarged, sclerotic mandible, broad clavicles and ribs, and diaphyseal undermodeling of the tubular bones. Metaepiphyseal sclerosis or longitudinal striation was found in the long bones. Metaphyseal equivalents of the axial skeleton showed dense osteosclerosis. These clinical and radiological manifestations overlapped with those of Lenz-Majewski syndrome. Unlike the classical phenotype of the disorder, however, he did not show brachymesophalangy with proximal symphalangism or growth failure. The present case may be considered to fall in the mildest end in the phenotypic continuum of Lenz-Majewski syndrome, suggesting that the clinical spectrum of the disorder may be broader than currently thought.