Genotype and clinical care correlations in craniosynostosis: findings from a cohort of 630 Australian and New Zealand patients

Craniosynostosis is one of the most common craniofacial disorders encountered in clinical genetics practice, with an overall incidence of 1 in 2,500. Between 30% and 70% of syndromic craniosynostoses are caused by mutations in hotspots in the fibroblast growth factor receptor (FGFR) genes or in the TWIST1 gene with the difference in detection rates likely to be related to different study populations within craniofacial centers. Here we present results from molecular testing of an Australia and New Zealand cohort of 630 individuals with a diagnosis of craniosynostosis. Data were obtained by Sanger sequencing of FGFR1, FGFR2, and FGFR3 hotspot exons and the TWIST1 gene, as well as copy number detection of TWIST1. Of the 630 probands, there were 231 who had one of 80 distinct mutations (36%). Among the 80 mutations, 17 novel sequence variants were detected in three of the four genes screened. In addition to the proband cohort there were 96 individuals who underwent predictive or prenatal testing as part of family studies. Dysmorphic features consistent with the known FGFR1-3/TWIST1-associated syndromes were predictive for mutation detection. We also show a statistically significant association between splice site mutations in FGFR2 and a clinical diagnosis of Pfeiffer syndrome, more severe clinical phenotypes associated with FGFR2 exon 10 versus exon 8 mutations, and more frequent surgical procedures in the presence of a pathogenic mutation. Targeting gene hot spot areas for mutation analysis is a useful strategy to maximize the success of molecular diagnosis for individuals with craniosynostosis.

Molecular characterisation of SMARCB1 and NF2 in familial and sporadic schwannomatosis

BACKGROUND

Schwannomatosis is a rare condition characterised by multiple schwannomas and lack of involvement of the vestibular nerve. A recent report identified bi-allelic mutations in the SMARCB1/INI1 gene in a single family with schwannomatosis. We aimed to establish the contribution of the SMARCB1 and the NF2 genes to sporadic and familial schwannomatosis in our cohort.

METHODS

We performed DNA sequence and dosage analysis of SMARCB1 and NF2 in 28 sporadic cases and 15 families with schwannomatosis.

RESULTS

We identified germline mutations in SMARCB1 in 5 of 15 (33.3%) families with schwannomatosis and 2 of 28 (7.1%) individuals with sporadic schwannomatosis. In all individuals with a germline mutation in SMARCB1 in whom tumour tissue was available, we detected a second hit with loss of SMARCB1. In addition, in all affected individuals with SMARCB1 mutations and available tumour tissue, we detected bi-allelic somatic inactivation of the NF2 gene. SMARCB1 mutations were associated with a higher number of spinal tumours in patients with a positive family history (p = 0.004).

CONCLUSION

In contrast to the recent report where no NF2 mutations were identified in a schwannomatosis family with SMARCB1 mutations, in our cohort, a four hit model with mutations in both SMARCB1 and NF2 define a subset of patients with schwannomatosis.

Estimating the referral rate for cancer genetic assessment from a systematic review of the evidence

To estimate the optimal proportion of new patients diagnosed with cancer who require assessment and evaluation for familial cancer genetic risk, based on the best evidence available. We identified evidence of the patients who require assessment for familial genetic risk when diagnosed with cancer through extensive literature reviews and searches of guidelines. Epidemiological data on the distribution of cancer type, presence of a family history, age and other factors that influence referral for genetic assessment were identified. Decision trees were constructed to merge the evidence-based recommendations with the epidemiological data to calculate the optimal proportion of patients who should be referred. We identified 'high probability' and 'moderate probability' groups for having a genetic susceptibility. The proportion of patients diagnosed with cancer in Australia who have a high probability of having a genetic predisposition and who should be referred for genetic assessment is 1%. If the moderate probability group is also assessed this proportion increases to 6%. This model has identified the proportion of new patients diagnosed with cancer who should be referred for genetic assessment. This data is the first step in determining the resources required for provision of an adequate cancer genetic service.

Histopathology and fibrillin-1 distribution in severe early onset Marfan syndrome

Marfan syndrome (MFS) is an autosomal dominant condition which may involve the cardiovascular, ocular, skeletal, and other systems. Mutations causing MFS are found in the FBN1 gene, encoding fibrillin-1, an extracellular matrix protein involved in microfibril formation. In the most severe cases, mutations are generally found in exons 24-32, and children with these mutations usually die in the first years of life, of cardiopulmonary failure. We present clinical, molecular and histopathological studies on a patient with severe early onset MFS. He has a mutation in exon 25 of FBN1, a G>A transition at nucleotide position 3131 that converts the codon TGC, coding for cysteine at position 1044, to TAC, coding for tyrosine (C1044Y). This has resulted in abnormalities of the extracellular matrix and a severe clinical phenotype, although he has survived to the age of 14 years.

Principal mutation hotspot for central core disease and related myopathies in the C-terminal transmembrane region of the RYR1 gene

The congenital myopathies are a group of disorders characterised by the predominance of specific histological features observed in biopsied muscle. Central core disease and nemaline myopathy are examples of congenital myopathies that have specific histological characteristics but significantly overlapping clinical pictures. Central core disease is an autosomal dominant disorder with variable penetrance which has been linked principally to the gene for the skeletal muscle calcium release channel (RYR1). Two recent reports have identified the 3' transmembrane domain of this gene as a common site for mutations. Two other studies have reported single families that have features of both central core disease and nemaline myopathy (core/rod disease) caused by mutations in RYR1. Screening of the 3' region (exons 93-105) of the RYR1 gene for mutations in 27 apparently unrelated patients with either central core disease or core/rod disease by single strand conformation polymorphism analysis and DNA sequencing identified three described and nine novel mutations in 15 patients.

Dhr1p, a putative DEAH-box RNA helicase, is associated with the box C+D snoRNP U3

Putative RNA helicases are involved in most aspects of gene expression. All previously characterized members of the DEAH-box family of putative RNA helicases are involved in pre-mRNA splicing. Here we report the analysis of two novel DEAH-box RNA helicases, Dhr1p and Dhr2p, that were found to be predominantly nucleolar. Both genes are essential for viability, and MET-regulated alleles were therefore created. Depletion of Dhr1p or Dhr2p had no detectable effect on pre-mRNA splicing in vivo or in vitro. Both Dhr1p and Dhr2p were, however, required for 18S rRNA synthesis. Depletion of Dhr2p inhibited pre-rRNA cleavage at sites A(0), A(1), and A(2), while Dhr1p depletion inhibited cleavage at sites A(1) and A(2). No coprecipitation of snoRNAs was detected with ProtA-Dhr2p, but Dhr1p-ProtA was stably associated with the U3 snoRNA. Depletion of Dhr1p inhibited processing steps that require base pairing of U3 to the 5' end of the 18S rRNA. We speculate that Dhr1p is targeted to the preribosomal particles by the U3-18S rRNA interaction and is required for the structural reorganization of the rRNA during formation of the central pseudoknot.

Patient with a 22q11.2 deletion with no overlap of the minimal DiGeorge syndrome critical region (MDGCR)

The apparent lack of genotype/phenotype correlation in patients with the DiGeorge anomaly and velocardiofacial syndrome (DGA/VCFS; the "22q11 deletion syndrome") indicates a complex genetic condition. Most cases, whatever the phenotype, have a 1.5-3 Mb chromosomal deletion that includes the minimal DiGeorge critical region (MDGCR). Another potential critical region on 22q11 has been suggested based on two patients with distal deletions outside the MDGCR. We report on a patient with a VCFS phenotype who has a deletion, mapped by short tandem repeat polymorphic loci and fluorescence in situ hybridization analysis, distal to and not overlapping the MDGCR. This patient is deleted for several genes, including the T-box 1 gene (TBX1; a transcription regulator expressed early in embryogenesis) and catechol-O-methyltransferase (COMT; involved in neurotransmitter metabolism). We discuss the role these two genes may play in the clinical phenotype of the patient.

Detection of a novel missense mutation and second recurrent mutation in the CACNA1A gene in individuals with EA-2 and FHM

Mutations in the brain specific P/Q type Ca2+ channel alpha1 subunit gene, CACNA1A, have been identified in three clinically distinct disorders, viz. episodic ataxia type 2 (EA-2), familial hemiplegic migraine (FHM) and spinocerebellar ataxia 6 (SCA6). For individuals with EA-2, the mutations described thus far are presumed to result in a truncated protein product. Several different missense mutations have been identified in patients with FHM. At least two of these mutations have been identified on two different chromosome 19p13 haplotypes and thus represent recurrent mutations. In the present study, we have screened several individuals for mutations in all 47 exons in the CACNA1A gene by single-strand conformation analysis. We have characterised a novel missense mutation, G5260A, in exon 32 in a family segregating for EA-2. The consequence of this mutation is an amino acid substitution at a highly conserved position within the CACNA1A gene. This represents the first point mutation not resulting in a proposed truncated protein. Furthermore, this mutation has been detected in a family member with mild clinical signs including only migraine. Additionally, a second previously identified recurrent muta tion, C2272T, in exon 16 has been discovered in a patient with FHM.

Identification of the gene (SEDL) causing X-linked spondyloepiphyseal dysplasia tarda

Spondyloepiphyseal dysplasia tarda (SEDL; MIM 313400) is an X-linked recessive osteochondrodysplasia that occurs in approximately two of every one million people. This progressive skeletal disorder which manifests in childhood is characterized by disproportionate short stature with short neck and trunk, barrel chest and absence of systemic complications. Distinctive radiological signs are platyspondyly with hump-shaped central and posterior portions, narrow disc spaces, and mild to moderate epiphyseal dysplasia. The latter usually leads to premature secondary osteoarthritis often requiring hip arthroplasty. Obligate female carriers are generally clinically and radiographically indistinguishable from the general population, although some cases have phenotypic changes consistent with expression of the gene defect. The SEDL gene has been localized to Xp22 (refs 8,9) in the approximately 2-Mb interval between DXS16 and DXS987 (ref. 10). Here we confirm and refine this localization to an interval of less than 170 kb by critical recombination events at DXS16 and AFMa124wc1 in two families. In one candidate gene we detected three dinucleotide deletions in three Australian families which effect frameshifts causing premature stop codons. The gene designated SEDL is transcribed as a 2.8-kb transcript in many tissues including fetal cartilage. SEDL encodes a 140 amino acid protein with a putative role in endoplasmic reticulum (ER)-to-Golgi vesicular transport.

Gene localization for an autosomal dominant familial periodic fever to 12p13

We report gene localization in a family with a benign autosomal dominant familial periodic fever (FPF) syndrome characterized by recurrent fever associated with abdominal pain. The clinical features are similar to the disorder previously described as familial Hibernian fever, and they differ from familial Mediterranean fever (FMF) in that FPF episodes usually do not respond to colchicine and FPF is not associated with amyloidosis. Frequent recombination with the marker D16S2622, <1 Mb from FMF, at 16p13.3, excluded allelism between these clinically similar conditions. Subsequently, a semiautomated genome search detected linkage of FMF to a cluster of markers at 12p13, with a multipoint LOD score of 6.14 at D12S356. If penetrance of 90% is assumed, the FPF gene maps to a 19-cM interval between D12S314 and D12S364; however, if complete penetrance is assumed, then FPF maps to a 9-cM region between D12S314 and D12S1695. This interval includes the dentatorubropallidoluysian atrophy locus, which, with FPF, gave a maximum two-point LOD score of 3.7 at a recombination fraction of 0. This is the first of the periodic-fever genes, other than FMF, to be mapped. Positional candidate genes may now be selected for mutation analysis to determine the molecular basis for FPF. Together with the recent identification of the defective gene in FMF, identification of a gene for FPF might provide new insights into the regulation of inflammatory responses.

Anal anomalies: an uncommon feature of velocardiofacial (Shprintzen) syndrome?

We report three cases of velocardiofacial syndrome (VCFS) with anal anomalies who have deletions of the 22q11 region and a further case where the proband has VCFS clinically and her father has an anal anomaly. It is important to consider VCFS in the differential diagnosis of children with anal anomalies and to look for other features of the syndrome, such as asymmetrical crying facies, submucous cleft of the palate, developmental delay, cardiac anomalies, and hypoparathyroidism.

Velo-cardio-facial and partial DiGeorge phenotype in a child with interstitial deletion at 10p13--implications for cytogenetics and molecular biology

We report on a female with a interstitial deletion of 10p13 and a phenotype similar to that seen with the 22q deletion syndromes (DiGeorge/velo-cardio-facial). She had a posterior cleft palate, perimembranous ventricular septal defect, dyscoordinate swallowing, T-cell subset abnormalities, small ears, maxillary and mandibular hypoplasia, broad nasal bridge, deficient alae nasi, contractures of fingers and developmental delay. This could indicate homology of some developmental genes at 22q and 10p so that patients with the velocardiofacial phenotype who do not prove to be deleted on 22q are candidates for a 10p deletion.

Clinical features in 27 patients with Angelman syndrome resulting from DNA deletion

We report the clinical features in 27 Australasian patients with Angelman syndrome (AS), all with a DNA deletion involving chromosome 15(q11-13), spanning markers from D15S9 to D15S12, about 3 center dot 5 Mb of DNA. There were nine males and 18 females. All cases were sporadic. The mean age at last review (end of 1994) was 11 center dot 2 years (range 3 to 34 years). All patients were ataxic, severely retarded, and lacking recognisable speech. In all patients, head circumference (HC) at birth was normal but skewed in distribution, with 62 center dot 5% at the 10th centile. At last review HC was around the 50th centile in three patients (12 center dot 5%) while 15 had poor postnatal head growth. Short stature was not invariable, 5/26 (19%) were on or above the 50th centile. Hypotonia at birth was recorded in 15/24 (63%) and neonatal feeding difficulties were recorded in 20/26 (77%). Epilepsy was present in 26/27 (96%) with onset by the third year of life in 20 patients (83%). Improvement in epilepsy was reported in 11/16 patients (69%) with age. An abnormal EEG was reported in 25/25 patients. Hypopigmentation was present in 19/26 (73%). One patient had oculocutaneous albinism. Five patients could not walk independently. Of the remaining 22 who could walk, age of onset of walking ranged from 2 to 8 years. Disrupted sleep patterns were present in 18/21 patients (86%), with improvement in 9/12 patients (75%) over 10 years of age. The clinical features in this group of deletional AS patients were similar to previous reports, but these have not separated patients into subgroups based on DNA studies. In our group of deletional cases, 100% showed severe mental retardation, ataxic movements, absent language, abnormal EEG, happy disposition (noted in infancy in 95%), normal birth weight and head circumference at birth, and a large, wide mouth. These features occurred with a higher frequency than in AS patients as a whole. Our study also provided information on the evolution of the phenotype. The data can act as a benchmark for comparisons of AS resulting from other genetic mechanisms.

Neurofibromatosis/Noonan phenotype: a variable feature of type 1 neurofibromatosis

Since January 1989 we have ascertained patients with neurofibromatosis type 1 (NF1) as part of our genetic register in the North West of England. This register has now identified 453 affected cases from 235 families. The first 94 individuals were specifically examined for features of the Noonan phenotype. This was present in 12/94 sequentially identified individuals with NF1 including six individuals from three families. However, three cases occurred in a further family, where Noonan syndrome appeared to segregate separately from NF1. We have provided evidence for the chance association of Noonan syndrome and NF1 and that the Noonan phenotype occurs as a feature in some NF1 families. However, there is now little evidence of a separate NF1/Noonan syndrome entity or of NF1 features occurring in classical Noonan syndrome.

An interstitial deletion of chromosome 7(q35)

We describe a patient with developmental delay, mild dysmorphic features, and monosomy of 7q35. Only one other patient with an interstitial deletion of this band has been previously reported. A review of clinical features of these two children did not show similarities in dysmorphic features. Reports of patients with other 7q interstitial deletions are listed.

Tandem duplication within a neurofibromatosis type 1 (NF1) gene exon in a family with features of Watson syndrome and Noonan syndrome

Type 1 neurofibromatosis (NF1), Watson syndrome (WS), and Noonan syndrome (NS) show some overlap in clinical manifestations. In addition, WS has been shown to be linked to markers flanking the NF1 locus and a deletion at the NF1 locus demonstrated in a WS patient. This suggests either that WS and NF1 are allelic or that phenotypes arise from mutations in very closely linked genes. Here we provide evidence for the former by demonstrating a mutation in the NF1 gene in a family with features of both WS and NS. The mutation is an almost perfect in-frame tandem duplication of 42 bases in exon 28 of the NF1 gene. Unlike the mutations previously described in classical NF1, which show a preponderance of null alleles, the mutation in this family would be expected to result in a mutant neurofibromin product.

Neurofibromatosis type 1 (NF1): knowledge, experience, and reproductive decisions of affected patients and families

Eighty-one subjects (56 affected patients and 25 parents of isolated affected cases) from 63 families with neurofibromatosis type 1 (NF1) on the North Western Regional Genetic Family Register (NWRGFR) were interviewed. Patients were interviewed either before (n = 26) or after (n = 55) genetic counselling. In the group as a whole, knowledge of the clinical features and the genetic aspects of the condition was poor (mean score 7 within the range of 0 to 18). The following factors were significantly associated with higher knowledge: (1) genetic counselling, (2) higher social class, (3) child with NF1, (4) when NF1 had influenced reproductive decisions, (5) young age at diagnosis, and (6) member of a patient support group. The majority of the affected subjects perceived themselves to be more severely affected than by medical classification, with persons who had been diagnosed later in life, had a child with NF1, or who were concerned about the cosmetic aspects of the disease perceiving themselves to be more severely affected. Assessment of the psychosocial effects of NF1 at different stages of life showed that 63% of affected subjects experienced difficulties at school and 48% said that the condition, particularly cosmetic aspects, caused anxiety during adolescence (n = 54). These difficulties may have contributed to later problems with career attainment and confidence in relationships. Seventy-seven percent of parents stated that their child was experiencing difficulties at school relating to NF1 (n = 51). Of the subjects at risk of having a child with NF1 and who knew about NF1 before having their family (n = 32), 45% said that it had influenced their reproductive decisions. Of 29 subjects who were still considering children, 41% wished to have prenatal diagnosis in a future pregnancy, but only three subjects stated that they would terminate an affected pregnancy.

Dominantly inherited unilateral retinal dysplasia

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Population screening for fragile X

A screening programme to detect fragile X syndrome has been operating in New South Wales, Australia, since 1984. The aim of this programme is to find previously unidentified individuals with the syndrome so that their extended families can be properly informed of the risks before making decisions about childbearing. 14,225 individuals attending adult and child facilities for the intellectually handicapped have been screened, of whom 8172 have been offered testing for the fragile X syndrome with a 79% uptake of the service. 253 probands were found, and in the extended families 818 females at 25-100% risk of being carriers were interviewed and counselled. Continuing contact was maintained and prenatal diagnosis was offered. The effect of the programme was assessed in a subgroup of 90 individuals, most of whom were appreciative of the service and felt that they had been adequately informed. The influence of knowing the diagnosis and its genetic implications were also assessed, the main consequences being a 26% reduction in births and a 61% uptake of prenatal diagnosis. Improved techniques for diagnosis of fragile X have benefited the families identified and counselled, suggesting that systematic screening for fragile X should be an essential component of community genetic services.

Unbalanced 13;18 translocation and Williams syndrome

A 2 1/2 year old girl is reported with a de novo 13;18 unbalanced translocation and the facial features of Williams syndrome, subaortic stenosis, failure to thrive, and developmental delay. This case provides two candidate locations for the underlying molecular pathology of this sporadic syndrome. Williams syndrome is associated with intellectual and growth retardation, infantile feeding problems which may be associated with hypercalcaemia, cardiovascular abnormalities, a friendly, loquacious personality, and a typical facies. The cause is not known and only a few chromosome abnormalities have been reported in patients with the Williams syndrome phenotype. Many papers fail to mention chromosome studies. We report a girl with an unbalanced 13;18 translocation and the Williams syndrome phenotype.

Ectopia lentis et pupillae: the genetic aspects and differential diagnosis

Two sib pairs and a fifth child are described with autosomal recessive ectopia lentis et pupillae. Patients with this disorder need regular ophthalmic review, but do not have the skeletal and metabolic complications associated with other syndromes with ectopia lentis.

De novo ring chromosome 3: a new case with a mild phenotype

We report an 18 year old female with a de novo ring chromosome 3 found after investigation for short stature. Her karyotype was interpreted as 46,XX, r(3)(p26.2q29). Her phenotype is milder than previously reported cases and illustrates the mild end of the spectrum of the ring chromosome 3 phenotype.

The gene for Treacher Collins syndrome maps to the long arm of chromosome 5

Treacher Collins syndrome (TCS) is an autosomal dominant disorder of craniofacial development, the features of which include conductive hearing loss and cleft palate. We have studied 12 unrelated TCS families with multiple affected individuals for linkage to five chromosome 5 markers. There is strong evidence demonstrating linkage to three of these markers. Multipoint linkage analysis places the mutation causing TCS in the interval between the gene for the glucocorticoid receptor and the anonymous marker D5S22, with a maximum multipoint lod score of 9.1.

Reproduction of complex movements: the effects of the presence of vision during encoding or at recall

This study investigated the role of vision in the encoding and reproduction of movement. Kinaesthetic reproductions of a kinaesthetically presented two-dimensional movement were compared with reproductions where vision was present either during the standard or at reproduction. The main finding was that the presence of vision during the standard resulted in poorer accuracy and greater underestimation of movement size than when it was absent throughout or present during reproduction. The presence of vision during the standard, however, resulted in less distortion of the linear components of movement shape although no such effect was found for the angular components. The initial direction of movement was reproduced more accurately where visual experience of the movement was given, either during the standard or during reproduction.

Reproduction of complex two-dimensional movements as a function of mode of presentation

The experiment reported here examined the kinaesthetic reproduction of two-dimensional patterns from three different modes of presentation: kinaesthetic only, visual only and visual plus kinaesthetic. The patterns were open and consisted of three linear segments of different lengths. All reproductions tended to underestimate pattern size. Subjects who had received visual experience of the pattern with or without simultaneous kinaesthetic experience produced significantly greater underestimates than subjects who had not seen the patterns. This is discussed in terms of the dominance of vision over kinaesthesis, and differences in size perception in the two modalities. Least distortion of the pattern shape was found in the reproduction of subjects who had received both kinaesthetic and visual experience of the criterion.

Spatial location judgements by right and left-handers

An attempt was made to replicate the left-hand advantage found by Roy and Mackenzie (1978) for a bimanual thumb-positioning task. As in their experiment strongly right-handed male and female subjects took part, and in addition strongly left-handed male and female subjects took part. Their findings were not fully replicated. A weak left-hand advantage was found for only one of the three error measures used (constant error). Significant interactions of sex with handedness were found for absolute and constant error. The difficulty of replication and current findings are discussed in terms of possible variations in subject strategy which warrant further investigation.

Reproduction of End-Location and Distance of Movement in Early and Later Blinded Subjects

This study examined the ability of early and later blinded subjects to reproduce the end location and distance of preselected arm movements of two different amplitudes (approximately 30 degrees and approximately 60 degrees). Both groups were found to reproduce end location with greater accuracy and less variability than distance. The early blinded subjects were less accurate however, and more variable in their reproductions of both movement cues than the later blinded subjects. The complications of these findings for the role of visual representation in memory for movement are discussed.