Identification of biallelic LRRK1 mutations in osteosclerotic metaphyseal dysplasia and evidence for locus heterogeneity.

BACKGROUND: Osteosclerotic metaphyseal dysplasia (OSMD) is a unique form of osteopetrosis characterised by severe osteosclerosis localised to the bone ends. The mode of inheritance is autosomal recessive. Its genetic basis is not known. OBJECTIVE: To identify the disease gene for OSMD. METHODS AND RESULTS: By whole exome sequencing in a boy with OSMD, we identified a homozygous 7 bp deletion (c.5938_5944delGAGTGGT) in the LRRK1 gene. His skeletal phenotype recapitulated that seen in the Lrrk1-deficient mouse. The shared skeletal hallmarks included severe sclerosis in the undermodelled metaphyses and epiphyseal margins of the tubular bones, costal ends, vertebral endplates and margins of the flat bones. The deletion is predicted to result in an elongated LRRK1 protein (p.E1980Afs*66) that lacks a part of its WD40 domains. In vitro functional studies using osteoclasts from Lrrk1-deficient mice showed that the deletion was a loss of function mutation. Genetic analysis of LRRK1 in two unrelated patients with OSMD suggested that OSMD is a genetically heterogeneous condition. CONCLUSIONS: This is the first study to identify the causative gene of OSMD. Our study provides evidence that LRRK1 plays a critical role in the regulation of bone mass in humans.

Rate of complications among the recipients of intrathecal baclofen pump in Japan: a multicenter study.

OBJECTIVE: To evaluate the incidence of complications of intrathecal baclofen (ITB) therapy for spasticity in Japan, where a unique training course and nationwide registration are required. MATERIALS AND METHODS: An analysis of complications was performed in all patients who underwent ITB in Japan from 2005 to 2011. Prior to surgery, all the doctors involved took a one-day training course, which included hands-on training. Surgical techniques that avoided complications were emphasized. RESULTS: A total of 406 pumps were implanted in 400 patients (277 men, 123 women) having severe spasticity. Because this study is currently in progress, among the 400 patients, 78.3% (313/400) had finished a one-year observation follow-up. There were 369 adult and 31 juvenile (under 17 years old) patients, including 12 patients under nine years old. All-cause adverse events were seen in 148 patients (37%), and 93 (23.3%) of these were regarded as severe. Catheter problems were observed in 34 (8.5%) patients: catheter migration in 25 (6.3%), breakage in 6 (1.5%), obstruction in 2 (0.5%), kinking in 1 (0.3%), and dislodgement in 1 (0.3%). Pump trouble was observed in seven (1.8%) patients: alarm abnormality in one (0.3%), memory error in one (0.3%), delayed recovery in one (0.3%), rotation in one (0.3%), malfunction in one (0.3%), and abnormal infusion rate in two (0.6%). Device-related and surgical wound infection occurred in 12 patients (3%), and nine were regarded as severe. Leakage or subcutaneous accumulation of the cerebrospinal fluid was seen in 13 patients (3.3%). CONCLUSION: The requirement of taking of a training course before starting ITB seemed to reduce complications. Although there were surgery-related complications, the rate of complications in Japan appeared to be lower than those reported in larger series of ITB. However, whether the reported rates can be primarily ascribed to a mandatory training course requires further investigations.

Effect of exercise at the AT point for children with cerebral palsy.

Eleven children with spastic cerebral palsy (CP) who could walk underwent exercise at the anaerobic threshold (AT) point. The subjects exercised for 20 minutes per session, twice a week for a period ranging from 6 to 20 weeks. The subjects were divided into two groups. The leg exercise group contained six CP children who exercised on a cycle ergometer with average attendance of 1.8 days a week. The other five CP children constituted the arm exercise group and exercised using an arm cranking ergometer with average attendance of 1.5 days per week. After the exercise period, the oxygen uptake (VO2) at the AT point increased significantly in the children in the leg exercise group. On the other hand, the VO2 at the AT point did not change in children in the arm exercise group. These results demonstrate that cycle ergometer exercise at the AT point is effective in improving the physical endurance of children with CP. In contrast, arm exercises for children with CP seem to have little effect on increasing physical endurance.

Japanese founder duplications/triplications involving BHLHA9 are associated with split-hand/foot malformation with or without long bone deficiency and Gollop-Wolfgang complex.

BACKGROUND: Limb malformations are rare disorders with high genetic heterogeneity. Although multiple genes/loci have been identified in limb malformations, underlying genetic factors still remain to be determined in most patients. METHODS: This study consisted of 51 Japanese families with split-hand/foot malformation (SHFM), SHFM with long bone deficiency (SHFLD) usually affecting the tibia, or Gollop-Wolfgang complex (GWC) characterized by SHFM and femoral bifurcation. Genetic studies included genomewide array comparative genomic hybridization and exome sequencing, together with standard molecular analyses. RESULTS: We identified duplications/triplications of a 210,050 bp segment containing BHLHA9 in 29 SHFM patients, 11 SHFLD patients, two GWC patients, and 22 clinically normal relatives from 27 of the 51 families examined, as well as in 2 of 1,000 Japanese controls. Families with SHFLD- and/or GWC-positive patients were more frequent in triplications than in duplications. The fusion point was identical in all the duplications/triplications and was associated with a 4 bp microhomology. There was no sequence homology around the two breakpoints, whereas rearrangement-associated motifs were abundant around one breakpoint. The rs3951819-D17S1174 haplotype patterns were variable on the duplicated/triplicated segments. No discernible genetic alteration specific to patients was detected within or around BHLHA9, in the known causative SHFM genes, or in the exome. CONCLUSIONS: These results indicate that BHLHA9 overdosage constitutes the most frequent susceptibility factor, with a dosage effect, for a range of limb malformations at least in Japan. Notably, this is the first study revealing the underlying genetic factor for the development of GWC, and demonstrating the presence of triplications involving BHLHA9. It is inferred that a Japanese founder duplication was generated through a replication-based mechanism and underwent subsequent triplication and haplotype modification through recombination-based mechanisms, and that the duplications/triplications with various haplotypes were widely spread in Japan primarily via clinically normal carriers and identified via manifesting patients. Furthermore, genotype-phenotype analyses of patients reported in this study and the previous studies imply that clinical variability is ascribed to multiple factors including the size of duplications/triplications as a critical factor.

A pair of sibs with tibial hemimelia born to phenotypically normal parents.

Tibial hemimelia is a rare congenital anomaly characterized by deficiency of the tibia with relatively intact fibula. Tibial hemimelia is identified as a solitary disorder, or a part of more complex malformation syndromes. Although the majority of cases with tibial hemimelia are sporadic, affected families with possible autosomal dominant or autosomal recessive inheritance have been reported. Here we report a pair of sibs, 6- and 2-year-old Japanese boys, with tibial hemimelia born to unrelated, phenotypically normal parents. The type of tibial hemimelia and associated malformations of hands and feet was quite different between the brothers. The elder brother was compatible with the Gollop-Wolfgang complex, and the younger brother with tibial agenesis-ectrodactyly syndrome. Screening of mutation by direct sequencing of candidate genes including Sonic hedgehog, HOXD-11, and HOXD-12 was unable to identify a disease-causing mutation.

Self-assessed secondary difficulties among paralytic poliomyelitis and spinal cord injury survivors in Japan.

OBJECTIVE: To determine the time course of secondary worsening of difficulties (SWD) experienced by postpolio and spinal cord injury (SCI) subjects in the general population. DESIGN: Self-report survey. SETTING: Multicenter study in general community in Japan. PARTICIPANTS: A total of 662 postpolio and 736 SCI subjects who had had contact with some rehabilitation facility. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Respondents completed a questionnaire about demographic factors, physical complaints, activities of daily living (ADLs), social participation, and a visual analog scale of time course for difficulties (VAST-D) devised for the present study in which the subjects drew a single curve to indicate the lifetime course of disability as they perceived it. RESULTS: Signs of SWD in all extremities of the polio patients and in the upper extremities of the SCI subjects were visually shown by the VAST-D. Additionally, the prevalence of postpolio syndrome and SWD in the SCI group was estimated to be 55.3% and 45.1%, respectively. CONCLUSIONS: SWD was visually shown by the VAST-D in polio and SCI subjects.

Novel types of COMP mutations and genotype-phenotype association in pseudoachondroplasia and multiple epiphyseal dysplasia.

Mutations in the gene encoding cartilage oligomeric matrix protein ( COMP) cause two skeletal dysplasias, pseudoachondroplasia (PSACH) and multiple epiphyseal dysplasia (MED). More than 40 mutations have been identified; however, genotype-phenotype relationships are not well delineated. Further, mutations other than in-frame insertion/deletions and substitutions have not been found, and currently known mutations are clustered within relatively small regions. Here we report the identification of nine novel and three recurrent COMP mutations in PSACH and MED patients. These include two novel types of mutations; the first, a gross deletion spanning an exon-intron junction, causes an exon deletion. The second, a frameshift mutation that results in a truncation of the C-terminal domain, is the first known truncating mutation in the COMP gene. The remaining mutations, other than a novel exon 18 mutation, affected highly conserved aspartate or cysteine residues in the calmodulin-like repeat (CLR) region. Genotype-phenotype analysis revealed a correlation between the position and type of mutations and the severity of short stature. Mutations in the seventh CLR produced more severe short stature compared with mutations elsewhere in the CLRs ( P=0.0003) and elsewhere in the COMP gene ( P=0.0007). Patients carrying mutations within the five-aspartates repeat (aa 469-473) in the seventh CLR were extremely short (below -6 SD). Patients with deletion mutations were significantly shorter than those with substitution mutations ( P=0.0024). These findings expand the mutation spectrum of the COMP gene and highlight genotype-phenotype relationships, facilitating improved genetic diagnosis and analysis of COMP function in humans.