Maternal psychological reaction to newborn genetic screening for type 1 diabetes

OBJECTIVE

The purpose of this work was to describe levels of maternal anxiety, depressive symptoms, and perceptions of infant vulnerability associated with newborn genetic screening for susceptibility to type 1 diabetes.

PATIENTS AND METHODS

Mothers of infants tested at birth for genetic susceptibility to type 1 diabetes as part of a prospective study investigating potential environmental triggers of autoimmunity were recruited to this study. Three mother-infant cohorts were studied: 38 infants at increased genetic risk, 73 at low risk, and 76 who had not undergone testing. The Vulnerable Baby Scale, Edinburgh Postnatal Depression Scale, and state subscale of the State Trait Anxiety Inventory were administered at the 9-week, 4-month, and 1-year postnatal ages. Genetic-risk notification occurred at the 10-week postnatal age. Mothers whose infants had undergone genetic testing were also asked to subjectively rate how much they thought and worried about their child's genetic test result. Statistical analyses were conducted to test for differences in questionnaire scores among the 3 groups.

RESULTS

No difference among the groups was detected in Vulnerable Baby Scale or Edinburgh Postnatal Depression Scale scores using linear mixed-effects model analysis. Maternal anxiety was paradoxically slightly lower in the increased-risk group shortly after notification of results, but there were no significant differences among the groups by 1 year. Mothers of infants in the high-risk group reported thinking and worrying about their child's test result significantly more than mothers of low-risk infants at both time points after notification of results.

CONCLUSIONS

Newborn genetic screening to identify infants at risk for type 1 diabetes is not associated with elevated levels of maternal anxiety, depressive symptoms, or heightened perceptions of infant vulnerability. However, responses to subjective assessment questions suggest that it is possible that more subtle effects on mothers do occur, and this requires further investigation.

Otopalatodigital syndrome type 2 in two siblings with a novel filamin A 629G>T mutation: clinical, pathological, and molecular findings

Otopalatodigital syndrome type 2 (OPD2) is an uncommon X-linked condition characterized by dysmorphic facies, a skeletal dysplasia affecting the axial and appendicular skeleton and extraskeletal anomalies including malformations of the brain, heart, genitourinary system, and intestines. Missense mutations of the FLNA gene, which encodes for the protein filamin A, have recently been shown to cause OPD2 and the allelic syndromes otopalatodigital type 1, Melnick-Needles, and frontometaphyseal dysplasia. Collectively these conditions constitute the otopalatodigital spectrum disorders. We report on two sibs affected by OPD2. The diagnosis was achieved at autopsy of a macerated male stillborn with typical external and skeletal findings of OPD2. A subsequent pregnancy was terminated due to ultrasonographic findings resembling those observed in the previous sibling. Histopathological studies revealed osseus sclerosis and do not support the previously reported membranous ossification defect observed in this condition. Mutation analysis demonstrated a novel mutation, 629G>T, in FLNA that had arisen de novo in the mother. This missense mutation predicts the substitution C210F within the second calponin homology domain of the actin-binding domain of filamin A. The identical substitution has been recently identified in an analogous amino-acid position within the actin binding domain of beta-spectrin leading to hereditary spherocytosis. The observation that phenylalanine is normally present in the same position in other proteins (utrophin, dystrophin) but leads to disease when present in filamin A implies that the function and/or structure of these actin binding domains are not entirely equivalent.

Phenotypic overlap in Melnick-Needles, serpentine fibula-polycystic kidney and Hajdu-Cheney syndromes: a clinical and molecular study in three patients

Several disorders characterized primarily by anomalies of the skeleton have recently been shown to be caused by mutations in the X-linked gene, FLNA. One of these conditions, the Melnick-Needles syndrome exhibits a phenotype that shares overlap with that of serpentine fibula-polycystic kidney syndrome and the autosomal dominant condition, Hajdu-Cheney syndrome. Here, we describe three individuals with these diagnoses. The individual with serpentine fibula-polycystic kidney syndrome, the fifth case reported in the literature, exhibited wormian bones which further expands the phenotypic spectrum for this condition and extends the overlap with Hajdu-Cheney syndrome. All three members of the filamin gene family, FLNA, and its functionally related paralogues, FLNB and FLNC, were screened for pathogenic mutations in all three individuals. We found a mutation in FLNA in the individual with Melnick-Needles syndrome, but no pathogenic variants in any filamin gene in the two individuals with Hajdu-Cheney syndrome and serpentine fibula-polycystic kidney syndrome. Clinical and molecular evidence indicates that Melnick-Needles syndrome is aetiologically distinct from Hajdu-Cheney syndrome and serpentine fibula-polycystic kidney syndrome, but these two latter conditions share many clinical similarities and may prove to be allelic to one another.

Frontometaphyseal dysplasia: mutations in FLNA and phenotypic diversity

Frontometaphyseal dysplasia is an X-linked trait primarily characterized by a skeletal dysplasia comprising hyperostosis of the skull and modeling anomalies of the tubular bones. Extraskeletal features include tracheobronchial, cardiac, and urological malformations. A proportion of individuals have missense mutations or small deletions in the X-linked gene, FLNA. We report here our experience with comprehensive screening of the FLNA gene in a group of 23 unrelated probands (11 familial instances, 12 simplex cases; total affected individuals 32) with FMD. We found missense mutations leading to substitutions in the actin-binding domain and within filamin repeats 9, 10, 14, 16, 22, and 23 of filamin A in 13/23 (57%) of individuals in this cohort. Some mutations present with a male phenotype that is characterized by a severe skeletal dysplasia, cardiac, and genitourinary malformations that leads to perinatal death. Although no phenotypic feature consistently discriminates between females with FMD who are heterozygous for FLNA mutations and those in whom no FLNA mutation can be identified, there is a difference in the degree of skewing of X-inactivation between these two groups. This observation suggests that locus heterogeneity may exist for this disorder.

Otopalatodigital syndrome spectrum disorders: otopalatodigital syndrome types 1 and 2, frontometaphyseal dysplasia and Melnick-Needles syndrome

The term otopalatodigital syndrome spectrum disorders is an umbrella category that includes four phenotypically related conditions, otopalatodigital syndrome types 1 and 2, frontometaphyseal dysplasia and Melnick - Needles syndrome. The phenotype of these conditions in the male ranges from a severe perinatally lethal multiple malformation syndrome to a mild skeletal dysplasia. Most, but not all, instances of these conditions are associated by mutations in the X-linked gene encoding the cytoskeletal protein filamin A. Mutations in this gene are clustered, exhibit a strong genotype-phenotype correlation and are presumed to exert their effect by a gain-of-function mechanism.

Mutations in two regions of FLNB result in atelosteogenesis I and III

The filamins are a family of cytoplasmic proteins that bind to and organize actin filaments, link membrane proteins to the cytoskeleton, and provide a scaffold for signaling molecules. Mutations in the gene encoding filamin B (FLNB) cause a spectrum of osteochondrodysplasias, including atelosteogenesis type I (AOI) and atelosteogenesis type III (AOIII). AOI and AOIII are autosomal dominant lethal skeletal dysplasias characterized by overlapping clinical findings that include vertebral abnormalities, disharmonious skeletal maturation, hypoplastic long bones, and joint dislocations. Previous studies have shown that heterozygosity for missense mutations that alter the CH2 domain and repeat 6 region of filamin B produce AOI and AOIII. In this study, 14 novel missense mutations in FLNB were found in 15 unrelated patients with AOI and AOIII. The majority of the mutations resided in exon 2 and exon 3, which encode the CH2 domain of the actin-binding region of filamin B. The remaining mutations were found in exon 28 and exon 29, which encode repeats 14 and 15 of filamin B. These results show that clustering of mutations in two regions of FLNB produce AOI/AOIII, and highlight the important role of this cytoskeletal protein in normal skeletogenesis.

A molecular and clinical study of Larsen syndrome caused by mutations in FLNB

BACKGROUND

Larsen syndrome is an autosomal dominant osteochondrodysplasia characterised by large-joint dislocations and craniofacial anomalies. Recently, Larsen syndrome was shown to be caused by missense mutations or small inframe deletions in FLNB, encoding the cytoskeletal protein filamin B. To further delineate the molecular causes of Larsen syndrome, 20 probands with Larsen syndrome together with their affected relatives were evaluated for mutations in FLNB and their phenotypes studied.

METHODS

Probands were screened for mutations in FLNB using a combination of denaturing high-performance liquid chromatography, direct sequencing and restriction endonuclease digestion. Clinical and radiographical features of the patients were evaluated.

RESULTS AND DISCUSSION

The clinical signs most frequently associated with a FLNB mutation are the presence of supernumerary carpal and tarsal bones and short, broad, spatulate distal phalanges, particularly of the thumb. All individuals with Larsen syndrome-associated FLNB mutations are heterozygous for either missense or small inframe deletions. Three mutations are recurrent, with one mutation, 5071G-->A, observed in 6 of 20 subjects. The distribution of mutations within the FLNB gene is non-random, with clusters of mutations leading to substitutions in the actin-binding domain and filamin repeats 13-17 being the most common cause of Larsen syndrome. These findings collectively define autosomal dominant Larsen syndrome and demonstrate clustering of causative mutations in FLNB.

Mutations in FLNB cause boomerang dysplasia

Boomerang dysplasia (BD) is a perinatal lethal osteochondrodysplasia, characterised by absence or underossification of the limb bones and vertebrae. The BD phenotype is similar to a group of disorders including atelosteogenesis I, atelosteogenesis III, and dominantly inherited Larsen syndrome that we have recently shown to be associated with mutations in FLNB, the gene encoding the actin binding cytoskeletal protein, filamin B. We report the identification of mutations in FLNB in two unrelated individuals with boomerang dysplasia. The resultant substitutions, L171R and S235P, lie within the calponin homology 2 region of the actin binding domain of filamin B and occur at sites that are evolutionarily well conserved. These findings expand the phenotypic spectrum resulting from mutations in FLNB and underline the central role this protein plays during skeletogenesis in humans.

Postzygotic mutation and germline mosaicism in the otopalatodigital syndrome spectrum disorders

The otopalatodigital syndrome (OPD) spectrum disorders are a heterogeneous group of skeletal dysplasias caused by mutations in the X-linked gene, FLNA. All OPD spectrum disorders (otopalatodigital syndromes types 1 and 2, frontometaphyseal dysplasia and Melnick-Needles syndrome) exhibit significant interfamilial variability in their expressivity, especially in female subjects. Factors contributing to this may include allelic heterogeneity, variation in the degree of skewing of X inactivation or, conceivably, mosaicism for the underlying causative mutation. We report here monozygotic twin sisters who are discordant for the severe phenotype, Melnick-Needles syndrome, associated with the heterozygous mutation, 3596C>T. We also describe two brothers with otopalatodigital syndrome type 1 due to the FLNA mutation 620G>A. The mutation is not detectable in the blood leucocytes of their clinically unaffected mother, indicating that she is a germline mosaic for the condition. The description of somatic mutations and germline mosaicism in FLNA has implications for clinical and molecular diagnosis, phenotypic expression and genetic counseling of families with these disorders.

A new osteochondrodysplasia with severe osteopenia, preaxial polydactyly, clefting and dysmorphic features resembling filamin-related disorders

BACKGROUND

We report a 19-week gestation female foetus with a new syndrome characterised by increased nuchal translucency and severe micromelia with campomelia evident from the early second trimester.

METHODS AND RESULTS

Cytogenetic studies performed on amniocytes revealed a normal female karyotype. Autopsy after termination of pregnancy showed facial dysmorphism, cleft palate, bowed, shortened limbs, hypoplasia of the preaxial elements in all four limbs with accompanying accessory ossification centres in the feet, and severe calvarial underossification. A diagnosis of otopalatodigital syndrome type 2, associated with mutations in FLNA, a gene encoding the cytoskeletal protein filamin A, was considered but discarded due to the severity of micromelia, early lethality, and the presence of generalised osteopenia instead of hyperostosis. The degree of undermodelling and campomelia was reminiscent of another group of conditions that include atelosteogenesis types 1 and 3, caused by mutations in FLNB. Sequencing analysis did not reveal any pathogenic mutation in the three paralogous filamin genes: FLNA, FLNB and FLNC.

CONCLUSION

Clinical, radiological and cytogenetic findings suggest that this phenotype is a new entity whose aetiopathogenesis may be functionally related to the filaminopathies.

Filamin A: phenotypic diversity

Filamins cross-link the actin cytoskeleton into orthogonal networks and modulate the response of cells to their chemical and mechanical environment by regulating changes in shape and motility. Null mutations in FLNA, the gene that encodes filamin A, lead to defects in neuronal migration, vascular function and connective tissue integrity. By contrast, missense mutations in this same gene produce a spectrum of malformations in multiple organ systems, especially the skeleton. The production of such distinctly different phenotypes from loss- and gain-of-function mechanisms provokes questions as to how a ubiquitously expressed structural protein can subserve crucial but discrete roles during development in many organ systems.

Tufted apple bud moth (Lepidoptera: Tortricidae) management model for processing apples based on early season pheromone trap capture

Sixteen years of archived tufted apple bud moth, Platynota idaeusalis (Walker), trap capture data were compared with archived fruit injury data collected at the Penn State University Fruit Research and Extension Center to define the relationship of trap capture to fruit injury. Pheromone trap capture until 15 June was the best predictor of fruit injury at harvest. Using the regression equation of fruit injury on early season trap capture, and other assumptions about insecticide cost and fruit yield, a management model was developed for apple growers in the Mid-Atlantic region. When the model was tested on archived trap capture and fruit injury data, the results indicated that a grower would lose money on average by always treating and save money on average by never treating. By using the model, a grower could expect to save more money than by never treating. The model showed sensitivity to fruit price, insecticide price, and fruit yield.

Newborn screening: new developments, new dilemmas

Scientific and technological advances are lending pressure to expand the scope of newborn screening. Whereas this has great potential for improving child health, it also challenges our current perception of such programmes. Standard newborn screening programmes are clearly justified by the fact that early detection and treatment of affected individuals avoids significant morbidity and mortality. However, proposals to expand the scope and complexity of such testing are not all supported by a similar level of evidence for unequivocal benefit. We argue that screening for genetic susceptibility to complex disorders is inherently different from standard screening and, while of potential value, must be considered separately from conventional testing.

Molecular pathology of filamin A: diverse phenotypes, many functions

Defective cell signalling during embryonic development is a well-recognized modus operandi of mutations in genes that lead to congenital malformations. This signalling occurs within and around a dynamic cellular cytoskeleton that is continuously under modulating influences during morphogenesis. Evidence is accumulating to suggest that filamin A, an actin-binding protein and the product of one of three paralogous filamin genes in humans, represents a key molecule that connects such signalling events to modulation of the cellular cytoskeletal architecture. This review summarizes the clinical consequences of mutations in the gene encoding filamin A, FLNA. The molecular pathology of this gene suggests remarkable functional pleiotropy, indicative of diverse roles in embryonic, fetal and postnatal development.

Mutations of ephrin-B1 (EFNB1), a marker of tissue boundary formation, cause craniofrontonasal syndrome

Craniofrontonasal syndrome (CFNS) is an X-linked developmental disorder that shows paradoxically greater severity in heterozygous females than in hemizygous males. Females have frontonasal dysplasia and coronal craniosynostosis (fusion of the coronal sutures); in males, hypertelorism is the only typical manifestation. Here, we show that the classical female CFNS phenotype is caused by heterozygous loss-of-function mutations in EFNB1, which encodes a member of the ephrin family of transmembrane ligands for Eph receptor tyrosine kinases. In mice, the orthologous Efnb1 gene is expressed in the frontonasal neural crest and demarcates the position of the future coronal suture. Although EFNB1 is X-inactivated, we did not observe markedly skewed X-inactivation in either blood or cranial periosteum from females with CFNS, indicating that lack of ephrin-B1 does not compromise cell viability in these tissues. We propose that in heterozygous females, patchwork loss of ephrin-B1 disturbs tissue boundary formation at the developing coronal suture, whereas in males deficient in ephrin-B1, an alternative mechanism maintains the normal boundary. This is the only known mutation in the ephrin/Eph receptor signaling system in humans and provides clues to the biogenesis of craniosynostosis.

Mutations in the gene encoding filamin B disrupt vertebral segmentation, joint formation and skeletogenesis

The filamins are cytoplasmic proteins that regulate the structure and activity of the cytoskeleton by cross-linking actin into three-dimensional networks, linking the cell membrane to the cytoskeleton and serving as scaffolds on which intracellular signaling and protein trafficking pathways are organized (reviewed in refs. 1,2). We identified mutations in the gene encoding filamin B in four human skeletal disorders. We found homozygosity or compound heterozygosity with respect to stop-codon mutations in autosomal recessive spondylocarpotarsal syndrome (SCT, OMIM 272460) and missense mutations in individuals with autosomal dominant Larsen syndrome (OMIM 150250) and the perinatal lethal atelosteogenesis I and III phenotypes (AOI, OMIM 108720; AOIII, OMIM 108721). We found that filamin B is expressed in human growth plate chondrocytes and in the developing vertebral bodies in the mouse. These data indicate an unexpected role in vertebral segmentation, joint formation and endochondral ossification for this ubiquitously expressed cytoskeletal protein.

Somatic and germline mosaicism for a R248C missense mutation in FGFR3, resulting in a skeletal dysplasia distinct from thanatophoric dysplasia

In this communication, we report the identification of a mosaic R248C missense mutation in the IgII-III linker region of the gene encoding the fibroblast growth factor receptor-3 (FGFR3), in an individual who manifests a skeletal dysplasia and epidermal hyperplasia. By means of Denaturing High Performance Liquid Chromatography (DHPLC), we determined that 25% of her lymphocytes are heterozygous for this particular missense mutation in FGFR3, and that 12.5% of her lymphocyte-derived genomic DNA encodes a cysteine residue at this position. The proposita has disproportionate short stature, radial head dislocation, coxa vara, and bowing of some of the long bones, associated with an S-shaped deformity of the humerus, accompanied by widespread acanthosis nigricans in the integument. These features do not match any previously described skeletal dysplasia. Further, the proposita's only pregnancy ended in the delivery of a fetus manifesting a lethal short-limbed dwarfism with pulmonary hypoplasia, strongly suggestive of an undiagnosed thanatophoric dysplasia. These findings confirm the proposita to be a somatic and germline mosaic for this particular missense mutation in FGFR3. Thus far, all reported FGFR3 R248C mutations have resulted in thanatophoric dysplasia type I (TDI).

Localized mutations in the gene encoding the cytoskeletal protein filamin A cause diverse malformations in humans

Remodeling of the cytoskeleton is central to the modulation of cell shape and migration. Filamin A, encoded by the gene FLNA, is a widely expressed protein that regulates re-organization of the actin cytoskeleton by interacting with integrins, transmembrane receptor complexes and second messengers. We identified localized mutations in FLNA that conserve the reading frame and lead to a broad range of congenital malformations, affecting craniofacial structures, skeleton, brain, viscera and urogenital tract, in four X-linked human disorders: otopalatodigital syndrome types 1 (OPD1; OMIM 311300) and 2 (OPD2; OMIM 304120), frontometaphyseal dysplasia (FMD; OMIM 305620) and Melnick-Needles syndrome (MNS; OMIM 309350). Several mutations are recurrent, and all are clustered into four regions of the gene: the actin-binding domain and rod domain repeats 3, 10 and 14/15. Our findings contrast with previous observations that loss of function of FLNA is embryonic lethal in males but manifests in females as a localized neuronal migration disorder, called periventricular nodular heterotopia (PVNH; refs. 3-6). The patterns of mutation, X-chromosome inactivation and phenotypic manifestations in the newly described mutations indicate that they have gain-of-function effects, implicating filamin A in signaling pathways that mediate organogenesis in multiple systems during embryonic development.

Variable expression of campomelic dysplasia in a father and his 46, XY daughter

Campomelic dysplasia (CD, MIM 114290) is characterised by widespread osseous abnormalities including bowing of the long bones, dysplasia of the cartilage of the tracheobronchial tree, and neurological abnormalities leading to high perinatal lethality. A majority of karyotypic males present as phenotypic females. The disorder has only recently been categorised as a dominantly transmitted entity after demonstration of heterozygous mutations in the SOX9 gene on chromosome 17q24.3 or translocations associated with breakpoints upstream of this gene. Despite this mode of transmission, only two well-documented instances of parent-child transmission of the disorder have been described. We report a man of normal intelligence with mild phenotypic and radiological appearances of CD. His first-born child, a phenotypic female with a 46,XY karyotype, presented with significantly more severe skeletal and neurological involvement. Parents of individuals with CD should be examined for minimal manifestations of the disorder, which may represent phenotypic variability in the syndrome or somatic mosaicism.

Dominant intermediate Charcot-Marie-Tooth neuropathy maps to chromosome 19p12-p13.2

The hereditary disorders of peripheral nerve form one of the most common groups of human genetic diseases, collectively called Charcot-Marie-Tooth (CMT) neuropathy. Using linkage analysis we have identified a new locus for a form of CMT that we have called "dominant intermediate CMT" (DI-CMT). A genomewide screen using 383 microsatellite markers showed strong linkage to the short arm of chromosome 19 (maximum LOD score 4.3, with a recombination fraction (straight theta) of 0, at D19S221 and maximum LOD score 5.28, straight theta=0, at D19S226). Haplotype analysis performed with 14 additional markers placed the DI-CMT locus within a 16.8-cM region flanked by the markers D19S586 and D19S546. Multipoint linkage analysis suggested the most likely location at D19S226 (maximum multipoint LOD score 6.77), within a 10-cM confidence interval. This study establishes the presence of a locus for DI-CMT on chromosome 19p12-p13.2.

Linkage of otopalatodigital syndrome type 2 (OPD2) to distal Xq28: evidence for allelism with OPD1

Otopalatodigital syndrome type 1 (OPD1) is an X-linked semidominant condition characterized by malformations of the skeleton, auditory apparatus, and palate. Previous studies have established linkage to a 16-cM region of Xq27-q28. A proposed allelic variant of OPD1, termed "OPD2," is associated with a more severe, frequently lethal phenotype with visceral and brain anomalies in addition to skeletal, auditory, and palatal defects. We report linkage of the OPD2 phenotype to a 2-cM region of distal Xq28 in a Maori kindred, with a maximum multipoint LOD score of 3.31 between the markers DXS1073 and DXS1108. This provides support for allelism between OPD1 and OPD2 and reduces the size of the disease interval to 1.8-2.1 Mb. We also demonstrate that female carriers of this disorder exhibit skewed inactivation that segregates with the high-risk haplotype and may be inversely related to the severity with which they manifest features of the disorder.

Hypogonadotrophic hypogonadism in Roifman syndrome

The combination of spondyloepiphyseal dysplasia, humoral immune deficiency, growth retardation, intellectual deficit and characteristic facial dysmorphism has recently been delineated as a discrete disorder thus far only reported in males. This report describes a fifth individual with co-existent hypogonadotrophic hypogonadism, thereby expanding the phenotype and possibly offering insight into the genetic aetiology of this condition.

Macrocephaly--cutis marmorata telangiectatica congenita: report of five patients and a review of the literature

Cutis marmorata telangiectatica congenita (CMTC) is a cutaneous disorder often accompanied by additional anomalies, most commonly segmental overgrowth. Recently a clinically discrete condition has been described comprising CMTC and congenital macrocephaly together with pre- and post-natal macrosomia, segmental overgrowth, central nervous system malformations, connective tissue abnormalities and intellectual handicap. We describe the natural history of macrocephaly-CMTC (M-CMTC) syndrome in a further five patients including the oldest reported patient, a 22 year old. The addition of our five patients brings the total number of reported patients to 28 and now makes it possible to more accurately delineate the phenotype and the frequency of clinical manifestations. We add some further clinical associations to those previously described, including anomalies of the growth of hair and teeth, neuronal migration defects, dislocated hips and stridor. We discuss potential genetic mechanisms that might account for the pleiotropic manifestations of this apparently rare segmental overgrowth disorder.

Congenital hypertrichosis, osteochondrodysplasia, and cardiomegaly: Cantú syndrome

Cantú syndrome (hypertrichosis, osteochondrodysplasia, cardiomegaly) is a rare condition, previously reported in 13 patients. We report on two additional patients with this disorder. One of the patients had pulmonary hypertension of unknown cause which was responsive to steroid therapy. She also had unusual, deep plantar creases, not reported previously in Cantú syndrome. Autosomal recessive inheritance has been suggested previously on the basis of sib recurrence in one family and consanguinity in another. We have performed a segregation analysis based on all reported families to date; the data indicate autosomal recessive inheritance is unlikely. A new dominant mutation or microdeletion syndrome are more likely possibilities, sib recurrence possibly representing gonadal mosaicism.

An autosomal dominant or X-linked osteodysplastic disorder with severe cervical involvement

A disorder affecting bone and cartilage growth is described in a mother and her 3-year-old son. A dysplastic process involving the vertebral bodies, most pronounced in the cervical region and leading to cervical dislocation in the first of these two patients, is the most significant complication of this disorder. This entity appears unrelated to other previously described skeletal dysplasias with cervical kyphosis as a major manifestation. This disorder is most likely autosomal dominant.

Sotos syndrome and cutis laxa

Characteristics suggestive of connective tissue dysfunction have been described in Sotos syndrome and include joint hyperextensibility, pes planus, and a high arched palate. A variety of cutis laxa syndromes have also been described, some of them exhibiting mental retardation, but no reports have drawn an association with overgrowth or abnormal facies characteristic of Sotos syndrome. We report three patients with the anthropometric and dysmorphological appearance of classical Sotos syndrome in association with redundant skin folds, joint hypermobility, and, in two of the three, vesicoureteric reflux suggestive of a coexisting connective tissue disorder. All of the patients had a normal bone age suggesting that Sotos syndrome in its classically described form was not present and that this entity possibly reflects a related, perhaps allelic, condition.

Cerebrospinal fluid shunts in the management of behavioural problems in Sanfilippo syndrome (MPS III)

Severe behavioural disturbance is a very common feature of Sanfilippo syndrome (mucopolysaccharidosis III, MPSIII), and one of the more difficult aspects of the disease to treat. We describe a series of six patients with MPS III who had cerebrospinal shunts inserted in an attempt to ameliorate behaviour that had proved refractory to conventional treatment. Symptoms improved significantly in all six but removal of the shunt was necessitated in one patient due to shunt blockage and infection.

CONCLUSION

Our experience suggests cerebrospinal fluid shunting should be formally evaluated as an adjunct to conventional forms of treatment of extreme behavioural disturbance in MPS III.

Zimmermann-Laband syndrome in an adult. Long-term follow-up of a patient with vascular and cardiac complications

Zimmermann-Laband syndrome (ZLS) is characterised by findings of coarse facial appearance, hepatosplenomegaly, and hirsutism often first observed in infancy, followed by the evolution during childhood of gingival fibromatosis, small joint hyperextensibility, and hypoplasia of the finger- and toenails. Intellectual deficit is variable. Some of these findings are suggestive of a storage disorder, but no biochemical defect has been identified. We report on a four decade follow-up of a male with ZLS who developed a cardiomyopathy and dilatation of the aortic root and arch, anomalies hitherto undescribed in this syndrome.

Early childhood growth in ethnic groups predisposed to NIDDM: a prospective study

Evidence is accumulating to suggest that the intrauterine environment may not only influence fetal growth and anthropometric indices at birth but also contribute to susceptibility to adult onset diseases such as non-insulin-dependent diabetes (NIDDM). We have followed up 77 out of 123 (65%) children at age 2 years 8 months derived from a population at high risk of NIDDM who were initially studied throughout pregnancy and birth to determine whether their weight, height, and measures of adiposity were predicted by maternal size, glycaemic control during pregnancy, or ethnicity. Adiposity was correlated with maternal pre-pregnancy weight and maternal serum triglyceride concentration. In contrast to the data gathered at birth, ethnic group did not predict any anthropometric variable except that South Asian children demonstrated faster weight gain in infancy compared to Polynesian or European subgroups.

The 4q-syndrome: delineation of the minimal critical region to within band 4q31

A consistent phenotype has been associated with deletion of the distal long arm of chromosome 4. An invariant requirement for the phenotype in cases described so far has been the deletion of material from within band 4q31 but few other cases have been described that further aid the delineation of the minimum critical region sufficient for the expression of the phenotype. We report a child with a small interstitial deletion within band 4q31 who exhibits most of the features of the established 4q-phenotype.

Protein adsorption to poly(ether urethane ureas) modified with acrylate and methacrylate polymer and copolymer additives

To understand better blood interactions with poly(ether urethane urea) (PEUU) materials, a radioimmunoassay and whole or diluted human plasma were used to characterize the presence of fibrinogen, immunoglobulin G, factor VIII/von Willebrand factor, Hageman factor (factor XII), and albumin on a PEUU formulation and on PEUU formulations modified with the amphiphilic additive Methacrol 2138F (co[diisopropylaminoethyl methacrylate (DIPAM)/decyl methacrylate] [3/1]), or with hydrophobic acrylate or methacrylate polymer or copolymer additives. The protein adsorption assay showed that PEUU films loaded or coated with Methacrol 2138F (Methacrol) or homopoly-DIPAM (h-DIPAM) adsorbed significantly lower amounts of the studied proteins than did either the base PEUU formulations or the PEUUs loaded with the more hydrophobic acrylate or methacrylate polymer additives. Experiments with Methacrol-loaded PEUUs, where the loading of Methacrol was varied from 0.25 wt% to 20.0 wt%, showed that the adsorption of each of the characterized proteins did not vary significantly throughout the Methacrol loading range, and that all Methacrol-loaded PEUU formulations adsorbed significantly lower amounts of the studied proteins than did the unloaded PEUU. Phase separation within the additive loaded PEUUs was characterized by scanning electron microscopy (SEM). The solubility parameters of the additives, as well as of the base PEUU, were calculated and used to interpret differences in phase separation of the additive modified PEUUs. The analysis showed that additives of lower solubility parameter phase-separated into fewer large microdroplets within the PEUU matrix. SEM analysis also showed that additive microdroplets were not present on the air side surface of loaded PEUUs. To explain the differences in protein adsorption to the air side of additive loaded PEUUs when compared to the base PEUU, it was assumed that the additives near this region of the solvent swollen PEUU matrix may have migrated to, at, or near the PEUU-air interface during film formation, creating an additive enriched PEUU surface region. Once at this surface region, it was suggested that dynamic surface reorientation in response to an aqueous medium ensured that the additives were able significantly to influence protein adsorption behavior only if they interacted with aqueous media more favorably than the PEUU.

Automated fluorometer/photometer system for homogeneous immunoassays

A fully automated bench-top clinical analyzer (OPTIMATE TM; Ames/Gilford) performs homogeneous fluorescent immunoassays, colorimetric immunoassays, and determinations of routine blood analytes; drugs, enzymes, metabolites, specific proteins, and hormones in serum. Unique features include a combination fluorescence/absorbance aspirating thermocuvette, a photon-counting fluorometer/photometer, a multi-reagent distribution valve to dispense as many as three reagents plus buffer, and a user-replaceable programmable memory cartridge for software updates. We have evaluated the performance of OPTIMATE substrate-labeled fluorescent immunoassays for gentamicin, tobramycin, amikacin, theophylline, phenytoin, phenobarbital, primidone, carbamazepine, and quinidine with this automated system. A sample throughput of 92 samples per hour is achieved by reading fixed-point fluorescence results every 39 s after an initial 4-min reaction period. Precision studies indicate typical CVs of less than or equal to 6% for mid-range controls. Standard curves can be reused for as long as two weeks before recalibration. With clinical samples, results by the OPTIMATE procedure correlated well (r greater than or equal to 0.97) with those by a reference method.

Automated fluorometer/photometer system for homogeneous immunoassays

A fully automated bench-top clinical analyzer (OPTIMATE TM; Ames/Gilford) performs homogeneous fluorescent immunoassays, colorimetric immunoassays, and determinations of routine blood analytes; drugs, enzymes, metabolites, specific proteins, and hormones in serum. Unique features include a combination fluorescence/absorbance aspirating thermocuvette, a photon-counting fluorometer/photometer, a multi-reagent distribution valve to dispense as many as three reagents plus buffer, and a user-replaceable programmable memory cartridge for software updates. We have evaluated the performance of OPTIMATE substrate-labeled fluorescent immunoassays for gentamicin, tobramycin, amikacin, theophylline, phenytoin, phenobarbital, primidone, carbamazepine, and quinidine with this automated system. A sample throughput of 92 samples per hour is achieved by reading fixed-point fluorescence results every 39 s after an initial 4-min reaction period. Precision studies indicate typical CVs of less than or equal to 6% for mid-range controls. Standard curves can be reused for as long as two weeks before recalibration. With clinical samples, results by the OPTIMATE procedure correlated well (r greater than or equal to 0.97) with those by a reference method.

Magnesium and the regulation of muscle contraction

There are a variety of Ca2+ binding sites in muscle (e.g., troponin, parvalbumin, myosin, and calmodulin) that may play a role in the regulation of muscle contraction an other enzymatic processes. since most of these proteins also bind Mg2+, it is important to consider the effect that the high free Mg2+ concentration (mM) found in muscle has on the Ca2+ binding properties of these sites. The major effect of Mg2+ is to greatly reduce the rate of Ca2+ binding to the sites that bind Mg2+ and Ca2+ competitively (Ca2+-Mg2+-type sites found in troponin, parvalbumin, and myosin, which would be essentially saturated with Mg2+ in a relaxed muscle) due to the slow dissociation of bound Mg2+. Thus during a transient increase in [Ca2+] similar to that which would occur during muscle activation, these sites would bind very little Ca2+ and, consequently, could not play a regulatory role. Even if Ca2+ were able to bind to these sites during muscle activation (e.g., if the free Mg2+ in muscle is lower than presumed), the dissociation of Ca2+ from these sites would be quite slow due to their very slow off rates for Ca2+, again making these sites unsuitable for participating in a rapid Ca2+-induced switching mechanisms. In contrast, the Ca2+-specific-type (regulatory) sites found in troponin and calmodulin do not have these restraints. The rate of Ca2+ binding to these sites is not affected by Mg2+ and the off rate of Ca2+ from these sites is very rapid due to their lower Ca2+ affinity. Thus, these sites are able to respond to rapid Ca2+ transients, an essential feature for any Ca2+ binding site that plays a regulator role.

The time-course of Ca2+ exchange with calmodulin, troponin, parvalbumin, and myosin in response to transient increases in Ca2+

We have modeled the time-course of Ca2+ binding to calmodulin, troponin, parvalbumin, and myosin in response to trains of transient increases in the free myoplasmic calcium ion concentration (pCa). A simple mathematical expression was used to describe each pCa transient, the shape and duration of which is qualitatively similar to those thought to occur in vivo. These calculations assumed that all individual metal binding sites are noninteracting and that Ca2+ bind competitively to the Ca2+-Mg2+ sites of troponin, parvalbumin, and myosin. All the on-and-off rate constants for both Ca2+ and Mg2+ were obtained either from the literature or from our own research. The percent saturation of the Ca2+-Mg2+ sites with Ca2+ was found to change very little in response to each pCa transient in the presence of 2.5 X 10(-3)M Mg2+. Our analysis suggests that the Ca2+ content of these sites is a measure of the intensity and frequency of recent muscle activity because large changes in the Ca2+ occupancy of these sites can occur with repeated stimulation. In contrast, large rapid changes in the amount of Ca2+ bound to the Ca2+-specific sites of troponin and calmodulin are induced by each pCa transient. Thus, only sites of the "Ca2+-specific" type can act as rapid Ca2+-regulatory sites in muscle. Fluctuation in the total amount of Ca2+ bound to these sites in response to various types of pCa transients further suggests that in vivo only about one-half to one-third of the total steady-state myofibrillar Ca2+-binding capacity exchanges Ca2+ during any single transient.

The calcium and magnesium binding sites on cardiac troponin and their role in the regulation of myofibrillar adenosine triphosphatase

The cardiac troponin (Tn) complex, consisting of a Ca2+-binding subunit (TnC), an inhibitory subunit (TnI), and a tropomyosin-binding subunit (TnT), has been reconstituted from purified troponin subunits isolated from bovine heart muscle. The Ca2+-binding properties of cardiac Tn were determined by equilibrium dialysis using either EGTA or EDTA to regulate the free Ca2+ concentration. Cardiac Tn binds 3 mol Ca2+/mol and contains two Ca2+-binding sites with a binding constant of 3 X 10(8) M-1 and one binding site with a binding constant of 2 X 10(6) M-1. In the presence of 4 mM MgC12, the binding constant of the sites of higher affinity is reduced to 3 X 10(7) M-1, while Ca2+ binding to the site at the lower affinity is unaffected. The two high affinity Ca2+-binding sites of cardiac Tn are analogous to the two Ca2+-Mg2+ sites of skeletal Tn, while the single low affinity site is similar to the two Ca2+-specific sites of skeletal Tn (Potter, J. D., and Gergely, J. (1975) J. Biol. Chem. 250, 4625-5633). The Ca2+-binding properties of the complex of TnC and TnI (1:1 molar ratio) were similar to those of Tn. Cardiac TnC also binds 3 mol of Ca2+/mol and contains two sites with a binding constant of 1 X 10(7) M-1 and a single site with a binding constant of 2 X 10(5) M-1. Assuming competition between Mg2+ and Ca2+ for the high affinity sites of TnC and Tn, the binding constants for Mg2+ were 0.7 and 3.0 X 10(3) M-1, respectively. The Ca2+ dependence of cardiac myofibrillar ATPase activity was similar to that of an actomyosin preparation regulated by the reconstituted troponin complex. Comparison by the Ca2+-binding properties of cardiac Tn and the cardiac myofibrillar ATPase activity as a function of [Ca2+] and at millimolar [Mg2+] suggests that activation of the ATPase occurs over the same range of [Ca2+] where the Ca2+-specific site of cardiac Tn binds Ca2+.

Calcium dependent regulation of brain and cardiac muscle adenylate cyclase

The very close interdependence of Ca2+ and hormones in the overall metabolism of cyclic nucleotides has recently been emphasized by Cheung. Clearly the results presented here show that [Ca2+] in the physiological range (less than 10(-7) M to greater than 10(-6) M) has profound effects on the activity of adenylate cyclase from both brain and cardiac muscle. Whereas both brain and cardiac cyclase exhibit a Ca2+ dependent inhibition (perhaps mediated by calmodulin), only the brain cyclase is activated by Ca2+ via calmodulin. With both cyclases there is an inverse relationship between the inhibition of cyclase and the activation of calmodulin dependent (cAMP and cGMP) phosphodiesterase as a function of Ca2+ concentration. Because the IC50's for Ca2+ are the same in both heart and brain, the possibility exists that the Ca2+ inhibitory site of both cyclases is similar and perhaps identical. Considering the ability of Ca2+ to both stimulate and inhibit cyclase, one could imagine that in different species, tissues, or regions of the same tissue, there could exist multiple populations of cyclase, that is a cyclase which would only show Ca2+ dependent inhibition, Ca2+ dependent stimulation, or the biphasic response to Ca2+ (FIGURE 7). The fact that Ca2+ still regulates adenylate cyclase after various stimuli (histamine, NaF, etc.) suggests that Ca2+ may function to regulate the cyclase over shorter time periods (regardless of its state of stimulation) and that other affectors of cyclase (e.g., hormones) would serve to regulate the cyclase over longer time periods.

A fluorescent probe study of Ca2+ binding to the Ca2+-specific sites of cardiac troponin and troponin C

Cardiac troponin C (C-TnC) was labeled with the sulfhydryl-specific fluorescent probe molecule 2-(4'-iodoacetamidoanilino)naphthalene-6-sulfonic acid at cysteine 35 and 84 to produce C-TnCIA. This modified protein binds Ca2+, undergoes Ca2+-induced increases in alpha helix, and forms a complex with other troponin subunits as does unlabeled C-TnC. C-TnCIA undergoes a small fluorescence decrease with Ca2+ or Mg2+ binding to the two high affinity Ca2+-Mg2+ sites of C-TnC and a large biphasic approximately 2.1-fold fluorescence increase with Ca2+ binding to two lower affinity Ca2+-specific sites with KCa of approximately 4.5 X 10(5) M-1 and approximately 5 X 10(2) M-1. C-TnCIA was formed in a complex with troponin I (TnI) and troponin T to form C-TnIA. This fluorescent reconstituted whole troponin undergoes a 25% decrease with Ca2+ binding to a Ca2+-specific site of KCa approximately 3 X 10(6) M-1. C-TnC, therefore, contains a single Ca2+-specific site of approximate equal affinity as the two Ca2+-specific regulatory sites of skeletal TnC. This Ca2+-specific site in C-TnC (like its two corresponding sites in S-TnC) undergoes an approximate 10-fold increase in affinity in whole troponin or when TnC is complexed with TnI. Since the two Ca2+-specific sites in skeletal troponin have been shown to be the regulatory sites of skeletal muscle contraction we suggest that this single Ca2+-specific site, of equal affinity, in C-TnC is the regulatory site of cardiac muscle contraction.

The effects of pH on Ca2+-activated force in frog skeletal muscle fibers

Ca2+-activated isometric force was recorded is skinned (sarcolemma mechanically removed) segments of frog skeletal muscle fibers immersed in bathing solution of different pH (5.0--10.5) and Ca2+ concentrations. Force in maximally activated fibers was near zero at pH 5.5, increased as pH increased to 7.5, remained relatively constant until pH 9.0 and then rapidly declined to zero by pH 10.5. The Ca2+ concentration at which 50% of maximum force was developed decreased 25-fold as pH increased from 5.5--7.5. The data also indicate that, while the fibers remains viable with acidosis, they deteriorate rapidly with alkalosis. These observations may be relevant clinically, since they parallel known effects of acidosis on cardiac contractility. The possible sites of action of H+ on the Ca2+-activated force generating mechanisms are discussed.