Marita Lipsanen-Nyman

Absence of a Paternally Inherited FOXP2 Gene in Developmental Verbal Dyspraxia

Mutations in FOXP2 cause developmental verbal dyspraxia (DVD), but only a few cases have been described. We characterize 13 patients with DVD--5 with hemizygous paternal deletions spanning the FOXP2 gene, 1 with a translocation interrupting FOXP2, and the remaining 7 with maternal uniparental disomy of chromosome 7 (UPD7), who were also given a diagnosis of Silver-Russell Syndrome (SRS). Of these individuals with DVD, all 12 for whom parental DNA was available showed absence of a paternal copy of FOXP2. Five other individuals with deletions of paternally inherited FOXP2 but with incomplete clinical information or phenotypes too complex to properly assess are also described. Four of the patients with DVD also meet criteria for autism spectrum disorder. Individuals with paternal UPD7 or with partial maternal UPD7 or deletion starting downstream of FOXP2 do not have DVD. Using quantitative real-time polymerase chain reaction, we show the maternally inherited FOXP2 to be comparatively underexpressed. Our results indicate that absence of paternal FOXP2 is the cause of DVD in patients with SRS with maternal UPD7. The data also point to a role for differential parent-of-origin expression of FOXP2 in human speech development.

Gene encoding a new RING-B-box-Coiled-coil protein is mutated in mulibrey nanism.

Mulibrey nanism (for muscle-liver-brain-eye nanism, MUL; MIM 253250) is an autosomal recessive disorder that involves several tissues of mesodermal origin, implying a defect in a highly pleiotropic gene. Characteristic features include severe growth failure of prenatal onset and constrictive pericardium with consequent hepatomegaly. In addition, muscle hypotonia, J-shaped sella turcica, yellowish dots in the ocular fundi, typical dysmorphic features and hypoplasia of various endocrine glands causing hormonal deficiency are common. About 4% of MUL patients develop Wilms′ tumour. MUL is enriched in the Finnish population, but is rare elsewhere. We previously assigned MUL to chromosome 17q22–q23 and constructed a physical contig over the critical MUL region. The region has now been further refined by haplotype analysis and new positional candidate genes have been localized. We identified a gene with four independent MUL-associated mutations that all cause a frameshift and predict a truncated protein. MUL is ubiquitously expressed and encodes a new member of the RING-B-box-Coiled-coil (RBCC) family of zinc-finger proteins, whose members are involved in diverse cellular functions such as developmental patterning and oncogenesis.

A Narrow Segment of Maternal Uniparental Disomy of Chromosome 7q31-qter in Silver-Russell Syndrome Delimits a Candidate Gene Region

Maternal uniparental disomy of chromosome 7 (matUPD7), the inheritance of both chromosomes from only the mother, is observed in approximately 10% of patients with Silver-Russell syndrome (SRS). It has been suggested that at least one imprinted gene that regulates growth and development resides on human chromosome 7. To date, three imprinted genes-PEG1/MEST, gamma2-COP, and GRB10-have been identified on chromosome 7, but their role in the etiology of SRS remains uncertain. In a systematic screening with microsatellite markers, for matUPD7 cases among patients with SRS, we identified a patient who had a small segment of matUPD7 and biparental inheritance of the remainder of chromosome 7. Such a pattern may be explained by somatic recombination in the zygote. The matUPD7 segment at 7q31-qter extends for 35 Mb and includes the imprinted gene cluster of PEG1/MEST and gamma2-COP at 7q32. GRB10 at 7p11.2-p12 is located within a region of biparental inheritance. Although partial UPD has previously been reported for chromosomes 6, 11, 14, and 15, this is the first report of a patient with SRS who has segmental matUPD7. Our findings delimit a candidate imprinted region sufficient to cause SRS.

The mutation spectrum in RECQL4 diseases.

Mutations in the RECQL4 gene can lead to three clinical phenotypes with overlapping features. All these syndromes, Rothmund–Thomson (RTS), RAPADILINO and Baller–Gerold (BGS), are characterized by growth retardation and radial defects, but RAPADILINO syndrome lacks the main dermal manifestation, poikiloderma that is a hallmark feature in both RTS and BGS. It has been previously shown that RTS patients with RECQL4 mutations are at increased risk of osteosarcoma, but the precise incidence of cancer in RAPADILINO and BGS has not been determined. Here, we report that RAPADILINO patients identified as carriers of the c.1390+2delT mutation (p.Ala420_Ala463del) are at increased risk to develop lymphoma or osteosarcoma (6 out of 15 patients). We also summarize all the published RECQL4 mutations and their associated cancer cases and provide an update of 14 novel RECQL4 mutations with accompanying clinical data.

Clinically Distinct Epigenetic Subgroups in Silver-Russell Syndrome: The Degree of H19 Hypomethylation Associates with Phenotype Severity and Genital and Skeletal Anomalies

CONTEXT The H19 imprinting control region (ICR), located on chromosome 11p15.5, has been reported hypomethylated in 20-65% of Silver-Russell syndrome (SRS) patients. OBJECTIVE We investigated the methylation status of 11p15.5 ICRs in SRS patients and children born small for gestational age (SGA) to clarify the relationship between phenotype and H19 methylation status. METHODS We performed methylation screens of the H19 and KCNQ1OT1 ICRs in 42 SRS patients, including seven maternal uniparental disomy of chromosome 7 patients, and 90 SGA children without SRS. Clinical data were evaluated from patient records, and seven hypomethylated patients were clinically and radiologically reexamined. RESULTS H19 ICR hypomethylation was found in 62% of SRS patients but in no SGA children. A clinical severity score demonstrated strong correlation between hypomethylation level and phenotype severity. Hypomethylation related to a more severe SRS phenotype, in which especially asymmetry and micrognathia were significantly more common. Extremely hypomethylated patients had abnormally high lumbar vertebrae, lumbar hypomobility, elbow subluxations, and distinct hand and foot anomalies. They also presented with congenital aplasia of the uterus and upper vagina, equivalent to the Mayer-Rokitansky-Küster-Hauser syndrome in females, and cryptorchidism and testicular agenesis in males. CONCLUSIONS We found a dose-response relationship between the degree of H19 hypomethylation and phenotype severity in SRS. We report for the first time the association of specific anomalies of the spine, elbows, hands and feet, and genital defects in SRS with severe H19 hypomethylation. Classical SRS features were found in H19 hypomethylation and milder symptoms in maternal uniparental disomy of chromosome 7, thus distinguishing two separate clinical and etiological subgroups.

Submicroscopic genomic alterations in Silver–Russell syndrome and Silver–Russell-like patients

Background Silver–Russell syndrome (SRS, OMIM 180860) features fetal and postnatal growth restriction and variable dysmorphisms. Genetic and epigenetic aberrations on chromosomes 7 and 11 are commonly found in SRS. However, a large fraction of SRS cases remain with unknown genetic aetiology. Methods 22 patients with a diagnosis of SRS (10 with H19 hypomethylation and 12 of unknown molecular aetiology) and their parents were studied with the Affymetrix 250K Sty microarray. Several analytical approaches were used to identify genomic aberrations such as copy number changes (CNCs), loss of heterozygosity (LOH) and uniparental disomy (UPD). Selected CNCs were verified with quantitative real-time PCR. Results The largest unambiguous CNCs were found in patients with previously molecularly unexplained SRS with relatively mild phenotypes: a heterozygous deletion of chromosome 15q26.3 including the IGF1R gene (2.6 Mb), an atypical distal 22q11.2 deletion (1.1 Mb), and a pseudoautosomal region duplication (2.7 Mb) in a male patient. LOH regions of potential relevance to the SRS phenotype were also identified. Importantly, no duplications or UPD of chromosomes 7 or 11 were identified. Conclusion Unexpected submicroscopic genomic events with pathogenic potential were found in three patients with molecularly unexplained SRS that was mild. The findings emphasise that SRS is heterogeneous in genetic aetiology beyond the major groups of H19 hypomethylation and maternal UPD7 and that unbiased genome-scale screens may reveal novel genotype–phenotype correlations.

Mulibrey nanism: clinical features and diagnostic criteria

Mulibrey nanism (MUL) is an autosomal recessive disease caused by mutations in the TRIM37 gene encoding the peroxisomal TRIM37 protein of unknown function. In this work, we analysed the clinical characteristics of 85 Finnish patients with MUL, most of whom were homozygous for the Finn major mutation of TRIM37. The patients’ hospital records from birth to the time of the diagnosis at age 0.02–52 years (median 2.1 years) were retrospectively analysed. All except four of the patients (95%) had a prenatal onset growth failure without postnatal catch up growth. The mean length standard deviation score (SDS) was −3.1 and −4.0 at birth and at diagnosis, respectively. In infancy, feeding difficulties, and respiratory tract infections were the most common problems. Congestive heart failure and pericardial constriction were diagnosed during infancy in 12% and 6% of the patients, respectively. At the time of the diagnosis, characteristic craniofacial features of scaphocephaly, facial triangularity, high and broad forehead, and low nasal bridge were evident in over 90% of the patients. In addition, practically all patients were gracile and had thin extremities. Other findings included a peculiar high-pitched voice (96%), yellowish dots in ocular fundi (79%), cutaneous naevi flammei (65%), hepatomegaly (45%), and fibrous dysplasia of long bones (25%). Mild muscular hypotonicity (68%) was the only neurological abnormality. The clinical features of the Finnish patients with MUL formed a distinct entity. The most consistent findings were growth failure and characteristic craniofacial features. However, organ manifestations varied considerably in early childhood. Based on these findings, we propose new diagnostic criteria for MUL.

The TRIM37 Gene Encodes a Peroxisomal RING-B-Box-Coiled-Coil Protein: Classification of Mulibrey Nanism as a New Peroxisomal Disorder

Mulibrey nanism is a rare growth disorder of prenatal onset caused by mutations in the TRIM37 gene, which encodes a RING-B-box-coiled-coil protein. The pathogenetic mechanisms of mulibrey nanism are unknown. We have used transiently transfected cells and antibodies raised against the predicted TRIM37 protein to characterize the TRIM37 gene product and to determine its intracellular localization. We show that the human TRIM37 cDNA encodes a peroxisomal protein with an apparent molecular weight of 130 kD. Peroxisomal localization is compromised in mutant protein representing the major Finnish TRIM37 mutation but is retained in the protein representing the minor Finnish mutation. Colocalization of endogenous TRIM37 with peroxisomal markers was observed by double immunofluorescence staining in HepG2 and human intestinal smooth muscle cell lines. In human tissue sections, TRIM37 shows a granular cytoplasmic pattern. Endogenous TRIM37 is not imported into peroxisomes in peroxin 1 (PEX1(-/-)) and peroxin 5 (PEX5(-/-)) mutant fibroblasts but is imported normally in peroxin 7 (PEX7(-/-)) deficient fibroblasts, giving further evidence for a peroxisomal localization of TRIM37. Fibroblasts derived from patients with mulibrey nanism lack C-terminal TRIM37 immunoreactivity but stain normally for both peroxisomal matrix and membrane markers, suggesting apparently normal peroxisome biogenesis in patient fibroblasts. Taken together, this molecular evidence unequivocally indicates that TRIM37 is located in the peroxisomes, and Mulibrey nanism thus can be classified as a new peroxisomal disorder.

Insufficient growth hormone secretion is associated with metabolic syndrome after allogeneic stem cell transplantation in childhood.

The aim was to evaluate whether the metabolic syndrome associates with other endocrinopathies observed after allogeneic stem cell transplantation (SCT) in childhood. Thirty-one SCT long-term survivors, transplanted for leukemia (n=26) or nonmalignant hematologic diseases (n=5) were evaluated by oral glucose tolerance test and assessment of serum lipids at a median age of 15 (range 7 to 34) years. Hyperinsulinemia, hypertriglyceridemia, and abdominal obesity were required for the diagnosis of metabolic syndrome. Growth hormone (GH) secretion was evaluated either with GH releasing hormone and arginine (n=14), clonidine (n=15), or insulin-tolerance (n=2) test. A GH peak level of <20 mU/L was considered insufficient. The thyroid and gonadal functions were assessed. Twelve patients (39%) had metabolic syndrome. Nine out of 12 (75%) patients with metabolic syndrome had insufficient GH response in provocative testing as opposed to 6/19 (31%) of those without it (P=0.02). No difference was observed in thyroid or gonadal function between patients with versus without metabolic syndrome. In conclusion, metabolic syndrome is frequently associated with insufficient GH secretion in the SCT long-term survivors. This should implicate a close follow-up of the metabolic parameters in SCT patients with either frank GH insufficiency or signs of inadequate GH response in provocative testing.

Global analysis of uniparental disomy using high density genotyping arrays

Background: Uniparental disomy (UPD), the inheritance of both copies of a chromosome from a single parent, has been identified as the cause for congenital disorders such as Silver-Russell, Prader-Willi, and Angelman syndromes. Detection of UPD has largely been performed through labour intensive screening of DNA from patients and their parents, using microsatellite markers. Methods: We applied high density single nucleotide polymorphism (SNP) microarrays to diagnose whole chromosome and segmental UPD and to study the occurrence of continuous or interspersed heterodisomic and isodisomic regions in six patients with Silver-Russell syndrome patients who had maternal UPD for chromosome 7 (matUPD7). Results: We have devised a new high precision and high-throughput computational method to confirm UPD and to localise segments where transitions of UPD status occur. Our method reliably confirmed and mapped the matUPD7 regions in all patients in our study. Conclusion: Our results suggest that high density SNP arrays can be reliably used for rapid and efficient diagnosis of both segmental and whole chromosome UPD across the entire genome.