Unrelated Japanese Patients Research Articles

Linking LRP12 CGG repeat expansion to inherited peripheral neuropathy.

The causative genes for over 60% of inherited peripheral neuropathy (IPN) remain unidentified. This study endeavours to enhance the genetic diagnostic rate in IPN cases by conducting screenings focused on non-coding repeat expansions. We gathered data from 2424 unrelated Japanese patients diagnosed with IPN, among whom 1555 cases with unidentified genetic causes, as determined through comprehensive prescreening analyses, were selected for the study. Screening for CGG non-coding repeat expansions in LRP12, GIPC1 and RILPL1 genes was conducted using PCR and long-read sequencing technologies. We identified CGG repeat expansions in LRP12 from 44 cases, establishing it as the fourth most common aetiology in Japanese IPN. Most cases (29/37) exhibited distal limb weakness, without ptosis, ophthalmoplegia, facial muscle weakness or bulbar palsy. Neurogenic changes were frequently observed in both needle electromyography (97%) and skeletal muscle tissue (100%). In nerve conduction studies, 28 cases primarily showed impairment in motor nerves without concurrent involvement of sensory nerves, consistent with the phenotype of hereditary motor neuropathy. In seven cases, both motor and sensory nerves were affected, resembling the Charcot-Marie-Tooth (CMT) phenotype. Importantly, the mean CGG repeat number detected in the present patients was significantly shorter than that of patients with LRP12-oculopharyngodistal myopathy (p<0.0001). Additionally, GIPC1 and RILPL1 repeat expansions were absent in our IPN cases. We initially elucidate LRP12 repeat expansions as a prevalent cause of CMT, highlighting the necessity for an adapted screening strategy in clinical practice, particularly when addressing patients with IPN.

Systematic molecular analyses for 115 karyotypically normal men with isolated non-obstructive azoospermia.

Do copy-number variations (CNVs) in the azoospermia factor (AZF) regions and monogenic mutations play a major role in the development of isolated (non-syndromic) non-obstructive azoospermia (NOA) in Japanese men with a normal 46, XY karyotype? Deleterious CNVs in the AZF regions and damaging sequence variants in eight genes likely constitute at least 8% and approximately 8% of the genetic causes, respectively, while variants in other genes play only a minor role. Sex chromosomal abnormalities, AZF-linked microdeletions, and monogenic mutations have been implicated in isolated NOA. More than 160 genes have been reported as causative/susceptibility/candidate genes for NOA. Systematic molecular analyses were conducted for 115 patients with isolated NOA and a normal 46, XY karyotype, who visited our hospital between 2017 and 2021. We studied 115 unrelated Japanese patients. AZF-linked CNVs were examined using sequence-tagged PCR and multiplex ligation-dependent probe amplification, and nucleotide variants were screened using whole exome sequencing (WES). An optimized sequence kernel association test (SKAT-O), a gene-based association study using WES data, was performed to identify novel disease-associated genes in the genome. The results were compared to those of previous studies and our in-house control data. Thirteen types of AZF-linked CNVs, including the hitherto unreported gr/gr triplication and partial AZFb deletion, were identified in 63 (54.8%) cases. When the gr/gr deletion, a common polymorphism in Japan, was excluded from data analyses, the total frequency of CNVs was 23/75 (30.7%). This frequency is higher than that of the reference data in Japan and China (11.1% and 14.7%, respectively). Known NOA-causative AZF-linked CNVs were found in nine (7.8%) cases. Rare damaging variants in known causative genes (DMRT1, PLK4, SYCP2, TEX11, and USP26) and hemizygous/multiple-heterozygous damaging variants in known spermatogenesis-associated genes (TAF7L, DNAH2, and DNAH17) were identified in nine cases (7.8% in total). Some patients carried rare damaging variants in multiple genes. SKAT-O detected no genes whose rare damaging variants were significantly accumulated in the patient group. The number of participants was relatively small, and the clinical information of each patient was fragmentary. Moreover, the pathogenicity of identified variants was assessed only by in silico analyses. This study showed that various AZF-linked CNVs are present in more than half of Japanese NOA patients. These results broadened the structural variations of AZF-linked CNVs, which should be considered for the molecular diagnosis of spermatogenic failure. Furthermore, the results of this study highlight the etiological heterogeneity and possible oligogenicity of isolated NOA. This study was supported by Grants from the Japan Society for the Promotion of Science (21K19283 and 21H0246), the Japan Agency for Medical Research and Development (22ek0109464h0003), the National Center for Child Health and Development, the Canon Foundation, the Japan Endocrine Society, and the Takeda Science Foundation. The results of this study were based on samples and patient data obtained from the International Center for Reproductive Medicine, Dokkyo Medical University Saitama Medical Center, Koshigaya, Japan. The authors have no conflicts of interest to disclose. N/A.

The Etiology and Outcome of Area Postrema Syndrome in Childhood: Two Cases and a Literature Review

BackgroundArea postrema syndrome (APS), a rare childhood condition, manifests as intractable nausea and hiccups. APS has high diagnostic significance in neuromyelitis optica syndrome spectrum disorders (NMOSD) and can be the initial presentation of other critical diseases, including brainstem glioma. MethodsWe described two representative cases of unrelated Japanese patients with APS. An etiologic evaluation, including a detailed intracranial neuroradiological examination and autoantibodies assessment, was performed. We also reviewed the literature focusing on the prognosis of pediatric APS symptoms. ResultsA 14-year-old girl with aquaporin-4 antibody-positive NMOSD showed a good prognosis with immunotherapy, whereas another nine-year-old girl with irresectable medullary low-grade glioma had persistent symptoms for more than 10 years. All reported children aged >12 years were diagnosed with NMOSD, and patients aged <13 years showed heterogeneous etiologies. ConclusionsDistinctive time courses and neuroimaging features were key clinical findings for the diagnostic and therapeutic processes in these patients. This literature review highlights the wide spectrum and prognosis of pediatric-onset APS.

Three KINSSHIP syndrome patients with mosaic and germline AFF3 variants.

AFF3 at 2q11.2 encodes the nuclear transcriptional activator AF4/FMR2 Family Member 3. AFF3 constitutes super elongation complex like 3, which plays a role in promoting the expression of genes involved in neurogenesis and development. The degron motif in AFF3 with nine highly conserved amino acids is recognized by E3 ubiquitin ligase to induce protein degradation. Recently, AFF3 missense variants in this region and variants featuring deletion including this region were identified and shown to cause KINSSHIP syndrome. In this study, we identified two novel and one previously reported missense variants in the degron of AFF3 in three unrelated Japanese patients. Notably, two of these three variants exhibited mosaicism in the examined tissues. This study suggests that mosaic variants also cause KINSSHIP syndrome, showing various phenotypes.

Mutation screening of the DNAJC7 gene in Japanese patients with sporadic amyotrophic lateral sclerosis

DNAJC7 has recently been identified as an amyotrophic lateral sclerosis (ALS) gene via large-scale exome analysis, and its involvement in ALS is still unclear in various populations. This study aimed to determine the frequencies and characteristics of the DNAJC7 variants in a Japanese ALS cohort. A total of 807 unrelated Japanese patients with sporadic ALS were screened via exome analysis. In total, we detected six rare missense variants and one splice-site variant of the DNAJC7 gene, which are not reported in the Japanese public database. Furthermore, the missense variants are located around the TPR domain, which is important for the function of DNAJC7. The total frequency of the DNAJC7 variants in Japanese ALS patients was estimated at 0.87%. Collectively, these results suggest that variants of DNAJC7 are rare cause of Japanese patients with sporadic ALS.

Genetic background in late-onset sensorineural hearing loss patients

Genetic testing for congenital or early-onset hearing loss patients has become a common diagnostic option in many countries. On the other hand, there are few late-onset hearing loss patients receiving genetic testing, as late-onset hearing loss is believed to be a complex disorder and the diagnostic rate for genetic testing in late-onset patients is lower than that for the congenital cases. To date, the etiology of late-onset hearing loss is largely unknown. In the present study, we recruited 48 unrelated Japanese patients with late-onset bilateral sensorineural hearing loss, and performed genetic analysis of 63 known deafness gene using massively parallel DNA sequencing. As a result, we identified 25 possibly causative variants in 29 patients (60.4%). The present results clearly indicated that various genes are involved in late-onset hearing loss and a significant portion of cases of late-onset hearing loss is due to genetic causes. In addition, we identified two interesting cases for whom we could expand the phenotypic description. One case with a novel MYO7A variant showed a milder phenotype with progressive hearing loss and late-onset retinitis pigmentosa. The other case presented with Stickler syndrome with a mild phenotype caused by a homozygous frameshift COL9A3 variant. In conclusion, comprehensive genetic testing for late-onset hearing loss patients is necessary to obtain accurate diagnosis and to provide more appropriate treatment for these patients.

Hypophosphatasia in Japan: ALPL Mutation Analysis in 98 Unrelated Patients.

Hypophosphatasia (HPP) is highly variable in clinical expression and is generally classified into six subtypes. Although it would be beneficial to be able to predict the clinical course from the ALPL genotype, studies on this issue are limited. Here, we aimed to clarify the features of Japanese HPP and the relationships between genotype and clinical manifestations. We analyzed 98 unrelated Japanese patients to investigate the percentage of each clinical form, frequently detected mutations, and the relationship between the genotype and phenotype. Some of the identified mutants were characterized by transfection experiments. Perinatal severe form was the most frequent (45.9%), followed by perinatal benign form (22.4%). Among the 196 alleles, p.Leu520ArgfsX86 (c.1559delT) was detected in 89 alleles, and p.Phe327Leu (c.979T>C) was identified in 23 alleles. All of the homozygotes for p.Leu520ArgfsX86 were classified into perinatal severe form, and patients carrying p.Phe327Leu in one of the alleles were classified into perinatal benign or odonto HPP. Twenty of the 22 patients with perinatal benign HPP were compound heterozygous for p.Phe327Leu and another mutation. Most patients with odonto HPP were found to be monoallelic heterozygotes for dominant-negative mutations or compound heterozygotes with mutants having residual activity. The high prevalence of p.Leu520ArgfsX86 and p.Phe327Leu mutations might underlie the high rate of perinatal severe and perinatal benign forms, respectively, in Japanese HPP. Although ALPL genotyping would be beneficial for predicting the clinical course to an extent, the observed phenotypical variability among patients sharing the same genotypes suggests the presence of modifiers.

A deep intronic mutation of c.1166-285 T > G in SLC46A1 is shared by four unrelated Japanese patients with hereditary folate malabsorption (HFM)

Hereditary folate malabsorption (HFM) is an autosomal recessive disease caused by mutations in SLC46A1 encoding the proton-coupled folate transporter (PCFT). HFM patients present with various clinical features including megaloblastic anemia, thrombocytopenia, combined immunodeficiency and neurodevelopmental disorders. In this study, we report the same deep intronic mutation of c.1166-285 T > G shared by four unrelated Japanese patients with HFM. This mutation was shown to generate a cryptic splice donor site for a 168-bp insertion of intron 3 sequences, leading to premature termination in the middle of this insertion. This mutation could be a founder mutation in the Japanese population, but also could be a hot-spot and could be present in undiagnosed HFM patients worldwide because of the difficulty to detect this mutation.

Rapid screening of copy number variations in STRC by droplet digital PCR in patients with mild-to-moderate hearing loss

Copy number variations (CNVs) are commonly reported in STRC, the causal gene for DFNB16. Various techniques are used clinically for CNV detection, and droplet digital PCR (ddPCR) provides highly precise absolute quantification of DNA copy number. We aimed to validate the feasibility and efficiency of ddPCR in combination with long-range PCR (LR-PCR) in identifying CNVs and mutations in STRC. Additionally, we determined the frequency of CNVs and mutations in STRC in Japanese patients with mild-to-moderate hearing loss. We evaluated 84 unrelated Japanese patients with mild-to-moderate bilateral idiopathic or autosomal recessive nonsyndromic sensorineural hearing loss. The ratio of STRC copy number to the copy number of the internal control RPP30 ranged from 0.949 to 1.009 (0.989 ± 0.017) in 77 patients; it ranged from 0.484 to 0.538 (0.509 ± 0.024) in five patients and was 0.000 in two patients, indicating heterozygous and homozygous deletions, respectively. The copy number deletion prevalence rates were 7.7% and 0.9% in the patients and healthy controls, respectively. In combination with LR-PCR, ddPCR revealed that at least three patients (3.6%) had STRC-related hearing loss. Detecting STRC CNVs by ddPCR was rapid, precise, and cost-effective and facilitated the identification of STRC CNVs.

A frequent variant in the Japanese population determines quasi-Mendelian inheritance of rare retinal ciliopathy

Hereditary retinal degenerations (HRDs) are Mendelian diseases characterized by progressive blindness and caused by ultra-rare mutations. In a genomic screen of 331 unrelated Japanese patients, we identify a disruptive Alu insertion and a nonsense variant (p.Arg1933*) in the ciliary gene RP1, neither of which are rare alleles in Japan. p.Arg1933* is almost polymorphic (frequency = 0.6%, amongst 12,000 individuals), does not cause disease in homozygosis or heterozygosis, and yet is significantly enriched in HRD patients (frequency = 2.1%, i.e., a 3.5-fold enrichment; p-value = 9.2 × 10−5). Familial co-segregation and association analyses show that p.Arg1933* can act as a Mendelian mutation in trans with the Alu insertion, but might also associate with disease in combination with two alleles in the EYS gene in a non-Mendelian pattern of heredity. Our results suggest that rare conditions such as HRDs can be paradoxically determined by relatively common variants, following a quasi-Mendelian model linking monogenic and complex inheritance.

Identification of de novo CSNK2A1 and CSNK2B variants in cases of global developmental delay with seizures.

Casein kinase 2 (CK2) is a serine threonine kinase ubiquitously expressed in eukaryotic cells and involved in various cellular processes. In recent studies, de novo variants in CSNK2A1 and CSNK2B, which encode the subunits of CK2, have been identified in individuals with intellectual disability syndrome. In this study, we describe four patients with neurodevelopmental disorders possessing de novo variants in CSNK2A1 or CSNK2B. Using whole-exome sequencing, we detected two de novo variants in CSNK2A1 in two unrelated Japanese patients, a novel variant c.571C>T, p.(Arg191*) and a recurrent variant c.593A>G, p.(Lys198Arg), and two novel de novo variants in CSNK2B in Japanese and Malaysian patients, c.494A>G, p.(His165Arg) and c.533_534insGT, p.(Pro179Tyrfs*49), respectively. All four patients showed mild to profound intellectual disabilities, developmental delays, and various types of seizures. This and previous studies have found a total of 20 CSNK2A1 variants in 28 individuals with syndromic intellectual disability. The hotspot variant c.593A>G, p.(Lys198Arg) was found in eight of 28 patients. Meanwhile, only five CSNK2B variants were identified in five individuals with neurodevelopmental disorders. We reviewed the previous literature to verify the phenotypic spectrum of CSNK2A1- and CSNK2B-related syndromes.

HLA-C*12:02 is a susceptibility factor in late-onset type of psoriasis in Japanese

Psoriasis is thought to be a multifactorial disease triggered by both genetic and environmental factors. The HLA-C locus on chromosome 6p21.33 remains the strongest susceptibility candidate locus in psoriasis. The strong association between psoriasis and the HLA-Cw6 allele has been well documented in various races. It is known that psoriatic patients with early onset are more likely to be familial and associated with HLA-Cw6. Familial occurrence of Japanese psoriasis is smaller than other populations. Furthermore, males are predominant over females in Japanese psoriasis. We investigated the relation between HLA-C alleles and age of onset, and in each gender for Japanese psoriasis, and discuss male predominance in the incidence of psoriasis in Japan. Four hundred forty six unrelated Japanese patients with psoriasis vulgaris and 557 sex- and age-matched unrelated Japanese healthy controls were investigated by genotyping. We confirmed the association between early-onset type of psoriasis with HLA-C*06:02 allele in Japanese. In addition, we detected the association between the late-onset type of psoriasis and the HLA-C*12:02 allele in Japanese. No significant differences in allele frequency were observed between females and males. Our results suggest that there is no genetic factor effect on male predominance in Japanese. In contract, the effect of environmental risk factors on the onset of Japanese psoriatic patients is stronger in males than in females. As a result, male predominant in psoriasis may occur in Japan.

Social Health Insurance-Based Simultaneous Screening for 154 Mutations in 19 Deafness Genes Efficiently Identified Causative Mutations in Japanese Hearing Loss Patients.

Sensorineural hearing loss is one of the most common neurosensory disorders in humans. The incidence of SNHL is estimated to be 1 in 500–1000 newborns. In more than half of these patients, the hearing loss is associated with genetic causes. In Japan, genetic testing for the patients with SNHL using the Invader assay to screen for 46 mutations in 13 deafness genes was approved by the Ministry of Health, Labour and Welfare for inclusion in social health insurance coverage in 2012. Furthermore, from August 2015, this genetic testing has been expanded to screen for 154 mutations in 19 deafness genes using targeted genomic enrichment with massively parallel DNA sequencing combined with the Invader assay and TaqMan genotyping. For this study we analyzed 717 unrelated Japanese hearing loss patients. The total allele frequency of 154 mutations in 19 deafness genes was 32.64% (468/1434) and the total numbers of cases associated with at least one mutation was 44.07% (316/717). Among these, we were able to diagnose 212 (30%) patients, indicating that the present screening could efficiently identify causative mutations in hearing loss patients. It is noteworthy that 27 patients (3.8%) had coexistent multiple mutations in different genes. Five of these 27 patients (0.7%, 5/717 overall) were diagnosed with genetic hearing loss affected by concomitant with responsible mutations in more than two different genes. For patients identified with multiple mutations in different genes, it is necessary to consider that several genes might have an impact on their phenotypes.

Growth hormone receptor gene variant and three-dimensional mandibular morphology.

To examine the relationship between three-dimensional mandibular morphology and growth hormone receptor (GHR) gene variants in a healthy Japanese population. The subjects, who were unrelated Japanese orthodontic patients, consisted of 64 men and 114 women. Using the Taqman genotyping assay, GHR gene rs6184 and rs6180 variants were detected in genomic DNA extracted from saliva. Mandibular volume and length were measured from cone-beam computed tomography images that were analyzed using Analyze image-processing software. The relationship between GHR gene variants and three-dimensional mandibular morphology was statistically examined. Statistical significance for the relationship between the distance between the left and right coronoid processes and rs6180 was noted (P < .05). Our results indicate that the GHR variant rs6180 is associated with the distance between the left and right coronoid process in the Japanese subjects.

Mutations in MME cause an autosomal-recessive Charcot-Marie-Tooth disease type 2.

ObjectiveThe objective of this study was to identify new causes of Charcot–Marie–Tooth (CMT) disease in patients with autosomal‐recessive (AR) CMT.MethodsTo efficiently identify novel causative genes for AR‐CMT, we analyzed 303 unrelated Japanese patients with CMT using whole‐exome sequencing and extracted recessive variants/genes shared among multiple patients. We performed mutation screening of the newly identified membrane metalloendopeptidase (MME) gene in 354 additional patients with CMT. We clinically, genetically, pathologically, and radiologically examined 10 patients with the MME mutation.ResultsWe identified recessive mutations in MME in 10 patients. The MME gene encodes neprilysin (NEP), which is well known to be one of the most prominent beta‐amyloid (Aβ)‐degrading enzymes. All patients had a similar phenotype consistent with late‐onset axonal neuropathy. They showed muscle weakness, atrophy, and sensory disturbance in the lower extremities. All the MME mutations could be loss‐of‐function mutations, and we confirmed a lack/decrease of NEP protein expression in a peripheral nerve. No patients showed symptoms of dementia, and 1 patient showed no excess Aβ in Pittsburgh compound‐B positron emission tomography imaging.InterpretationOur results indicate that loss‐of‐function MME mutations are the most frequent cause of adult‐onset AR‐CMT2 in Japan, and we propose that this new disease should be termed AR‐CMT2T. A loss‐of‐function MME mutation did not cause early‐onset Alzheimer's disease. Identifying the MME mutation responsible for AR‐CMT could improve the rate of molecular diagnosis and the understanding of the molecular mechanisms of CMT. Ann Neurol 2016;79:659–672

Association of copy number polymorphisms at the promoter and translated region of COMT with Japanese patients with schizophrenia

Chromosome 22q11.2 deletion syndrome and genetic variations including single-nucleotide polymorphism (SNP) and copy number variation (CNV) in catechol-O-methyltransferase (COMT) situated at 22q11.2 remains controversial. Here, the genetic relationship between COMT and Japanese patients with schizophrenia was investigated by examining whether the SNPs correlated with schizophrenia based on a common disease-common variant hypothesis. Additionally, 22q11.2DS were screened based on a common disease-rare variant hypothesis; low-frequency CNVs situated at two COMT promoters and exons were investigated based on the low-frequency variants with an intermediate effect; and positive findings from the first stage were reconfirmed using a second-stage replication study including a larger sample size. Eight SNPs and 10 CNVs were investigated using Taqman SNP and CNV quantitative real-time polymerase chain reaction method. For the first-stage analysis, 513 unrelated Japanese patients with schizophrenia and 705 healthy controls were examined. For the second-stage replication study, positive findings from the first stage were further investigated using a larger sample size, namely 1,854 patients with schizophrenia and 2,137 controls. The first-stage analysis showed significant associations among schizophrenia, intronic SNP rs165774, CNV6 situated at promoter 1, CNV8 at exon 6, and CNV9 at exon 7. The second-stage study showed that intronic SNP rs165774 (χ(2) = 8.327, P = 0.0039), CNV6 (χ(2) = 19.66, P = 0.00005), and CNV8 (χ(2) = 16.57, P = 0.00025) were significantly associated with schizophrenia. Large and rare CNVs as well as low-frequency CNVs and relatively small CNVs, namely <30 kb in COMT, may be genetic risk factors for schizophrenia.

MLC1 mutations in Japanese patients with megalencephalic leukoencephalopathy with subcortical cysts.

Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is an autosomal recessive neurological disorder manifesting early onset macrocephaly and delayed-onset neurological deterioration. Characteristic radiological findings revealed by brain magnetic resonance imaging are the most important factors for obtaining a clinical diagnosis. In this study, we analyzed the causative gene, MLC1, in seven unrelated Japanese patients. The most common mutation in our study was p.S93L; this mutation was observed in 11 alleles (78.6%). The second most common mutation, p.A275D, was observed in two alleles (14.3%). A novel single-nucleotide deletion, c.578delG (p.V194Sfs*2), was identified in one allele. As the clinical severities of patients with MLC were variable even among those sharing identical genotypes, this condition may be modified by environmental factors, modifier genes or epigenetic factors.

HLA-C*12:02 is a susceptibility factor in late-onset type of psoriasis in Japanese.

Psoriasis is thought to be a multifactorial disease triggered by both genetic and environmental factors. The HLA-C locus on chromosome 6p21.33 remains the strongest susceptibility candidate locus in psoriasis. The strong association between psoriasis and the HLA-Cw6 allele has been well documented in various races. It is known that psoriatic patients with early onset are more likely to be familial and associated with HLA-Cw6. Familial occurrence of Japanese psoriasis is smaller than other populations. Furthermore, males are predominant over females in Japanese psoriasis. We investigated the relation between HLA-C alleles and age of onset, and in each gender for Japanese psoriasis, and discuss male predominance in the incidence of psoriasis in Japan. Four hundred forty six unrelated Japanese patients with psoriasis vulgaris and 557 sex- and age-matched unrelated Japanese healthy controls were investigated by genotyping. We confirmed the association between early-onset type of psoriasis with HLA-C*06:02 allele in Japanese. In addition, we detected the association between the late-onset type of psoriasis and the HLA-C*12:02 allele in Japanese. No significant differences in allele frequency were observed between females and males. Our results suggest that there is no genetic factor effect on male predominance in Japanese. In contract, the effect of environmental risk factors on the onset of Japanese psoriatic patients is stronger in males than in females. As a result, male predominant in psoriasis may occur in Japan.

Identification and Functional Characterization of Two Novel NPR2 Mutations in Japanese Patients With Short Stature

C-type natriuretic peptide-natriuretic peptide receptor B (NPR-B) signaling is critical for endochondral ossification, which is responsible for longitudinal growth in limbs and vertebrae. Biallelic NPR2 mutations cause acromesomelic dysplasia, type Maroteaux, which is bone dysplasia characterized by severe short stature and short limbs. A monoallelic NPR2 mutation has been suggested to mildly impair long bone growth. The goal of this study was to identify and characterize NPR2 mutations among Japanese patients with short stature. We enrolled 101 unrelated Japanese patients with short stature. NPR2 and NPPC were sequenced, and the identified variants were characterized in vitro. In two subjects, we identified two novel heterozygous NPR2 mutations (R110C and Q417E) causing a loss of C-type natriuretic peptide-dependent cGMP generation capacities and having dominant-negative effects. R110C was defective in trafficking from the endoplasmic reticulum to the Golgi apparatus. In contrast, Q417E showed clear cell surface expression. We identified heterozygous NPR2 mutations in 2% of Japanese patients with short stature. Our in vitro findings indicate that NPR2 mutations have a dominant negative effect, and their dominant-negative mechanisms vary corresponding to the molecular pathogenesis of the mutations.

Novel PAX9 Mutations Cause Non-syndromic Tooth Agenesis

PAX9 is a transcription factor expressed in the tooth mesenchyme during tooth morphogenesis. In Pax9-null mice, tooth development is arrested at the bud stage. In humans, heterozygous mutations in PAX9 have been associated with non-syndromic tooth agenesis, predominantly in the molars. Here, we report 2 novel mutations in the paired domain of PAX9, a three-nucleotide deletion (73-75 delATC) and a missense mutation (C146T), in two unrelated Japanese patients with non-syndromic tooth agenesis. The individual with the 73-75del ATC mutation was missing all maxillary molars and mandibular second and third molars. The individual with the C146T mutation was missing the mandibular central incisors, maxillary second premolars, and first molars, along with all second and third molars. Both mutations affected amino acids that are highly conserved among different species and are critical for DNA binding. When both mutants were transfected to COS7 cells, nuclear localization of PAX9 proteins was not affected. However, reduced expression of the mutant proteins and almost no transcriptional activity of the target BMP4 gene were observed, suggesting haploinsufficiency of PAX9 as the cause of non-syndromic tooth agenesis.