Pulmonary hypoplasia and persistent pulmonary hypertension in the newborn with homozygous α-thalassemia: a case report and review of the literature

The survival of infants with homozygous alpha-thalassemia, once considered a lethal diagnosis, is now possible through in utero and postnatal diagnostic and therapeutic interventions. We report the survival of a newborn with homozygous alpha-thalassemia complicated by pulmonary hypoplasia and persistent pulmonary hypertension, an association not previously reported.

A 1.5 million-base pair inversion polymorphism in families with Williams-Beuren syndrome

Williams-Beuren syndrome (WBS) is most often caused by hemizygous deletion of a 1.5-Mb interval encompassing at least 17 genes at 7q11.23 (refs. 1,2). As with many other haploinsufficiency diseases, the mechanism underlying the WBS deletion is thought to be unequal meiotic recombination, probably mediated by the highly homologous DNA that flanks the commonly deleted region. Here, we report the use of interphase fluorescence in situ hybridization (FISH) and pulsed-field gel electrophoresis (PFGE) to identify a genomic polymorphism in families with WBS, consisting of an inversion of the WBS region. We have observed that the inversion is hemizygous in 3 of 11 (27%) atypical affected individuals who show a subset of the WBS phenotypic spectrum but do not carry the typical WBS microdeletion. Two of these individuals also have a parent who carries the inversion. In addition, in 4 of 12 (33%) families with a proband carrying the WBS deletion, we observed the inversion exclusively in the parent transmitting the disease-related chromosome. These results suggest the presence of a newly identified genomic variant within the population that may be associated with the disease. It may result in predisposition to primarily WBS-causing microdeletions, but may also cause translocations and inversions.

KCNE1-like gene is deleted in AMME contiguous gene syndrome: identification and characterization of the human and mouse homologs

We describe the identification and characterization of a new gene deleted in the AMME contiguous gene syndrome. This gene is predominantly expressed in heart, skeletal muscle, spinal cord, and brain. Screening of placenta and NT2 cDNA libraries enabled us to obtain the 1.5-kb full-length transcript, which shows a 426-bp open reading frame. Since the resulting 142-amino-acid peptide has a single putative transmembrane domain and a weak but suggestive homology with KCNE1 (minK), a protein associated with the KCNQ1 potassium channel (KVLQT1), we named this new gene KCNE1-like (KCNE1L). To obtain greater insight into this new member of an apparently distinct protein family, we have identified and characterized the homologous mouse gene (Kcne1l), which encodes a peptide of 143 amino acids with 91% homology and 80% identity. The expression pattern of mouse Kcne1l in the developing embryo revealed strong signal in ganglia, in the migrating neural crest cells of cranial nerves, in the somites, and in the myoepicardial layer of the heart. The specific distribution in adult tissues, the putative channel function, and the expression pp6tern in the developing mouse embryo suggest that KCNE1L could be involved in the development of the cardiac abnormalities as well as of some neurological signs observed in patients with AMME contiguous gene syndrome.

PTEN mutation spectrum and genotype-phenotype correlations in Bannayan-Riley-Ruvalcaba syndrome suggest a single entity with Cowden syndrome

Germline mutations in the tumour suppressor gene PTEN have been implicated in two hamartoma syndromes that exhibit some clinical overlap, Cowden syndrome (CS) and Bannayan-Riley-Ruvalcaba syndrome (BRR). PTEN maps to 10q23 and encodes a dual specificity phosphatase, a substrate of which is phosphatidylinositol 3,4,5-triphosphate, a phospholipid in the phosphatidylinositol 3-kinase pathway. CS is characterized by multiple hamartomas and an increased risk of benign and malignant disease of the breast, thyroid and central nervous system, whilst the presence of cancer has not been formally documented in BRR. The partial clinical overlap in these two syndromes is exemplified by the hallmark features of BRR: macrocephaly and multiple lipomas, the latter of which occur in a minority of individuals with CS. Additional features observed in BRR, which may also occur in a minority of CS patients, include Hashimoto's thyroiditis, vascular malformations and mental retardation. Pigmented macules of the glans penis, delayed motor development and neonatal or infant onset are noted only in BRR. In this study, constitutive DNA samples from 43 BRR individuals comprising 16 sporadic and 27 familial cases, 11 of which were families with both CS and BRR, were screened for PTEN mutations. Mutations were identified in 26 of 43 (60%) BRR cases. Genotype-phenotype analyses within the BRR group suggested a number of correlations, including the association of PTEN mutation and cancer or breast fibroadenoma in any given CS, BRR or BRR/CS overlap family ( P = 0.014), and, in particular, truncating mutations were associated with the presence of cancer and breast fibroadenoma in a given family ( P = 0.024). Additionally, the presence of lipomas was correlated with the presence of PTEN mutation in BRR patients ( P = 0.028). In contrast to a prior report, no significant difference in mutation status was found in familial versus sporadic cases of BRR ( P = 0.113). Comparisons between BRR and a previously studied group of 37 CS families suggested an increased likelihood of identifying a germline PTEN mutation in families with either CS alone or both CS and BRR when compared with BRR alone ( P = 0.002). Among CS, BRR and BRR/CS overlap families that are PTEN mutation positive, the mutation spectra appear similar. Thus, PTEN mutation-positive CS and BRR may be different presentations of a single syndrome and, hence, both should receive equal attention with respect to cancer surveillance.

Elevated ambulatory blood pressure in 20 subjects with Williams syndrome

Previous studies report conflicting frequencies of hypertension in cohorts of patients with Williams syndrome (WS). We studied blood pressure (BP) in WS using 24-hour ambulatory BP monitoring. This technique reliably measures day- and nighttime BP in a subject's natural environment and provides better prognostic information on long-term risks of hypertension than casual BP determinations. Twenty WS subjects evaluated through a multidisciplinary WS clinic and 35 age and gender-matched controls were studied. We found that WS subjects had significantly higher ambulatory BP than controls. After controlling for age, sex, and weight, the diagnosis of WS added approximately 10 mmHg to mean daytime and nighttime BPs. Hypertension, as defined by elevated mean daytime BP, was present in 40% of WS subjects versus 14% of controls (P < 0.05); among the children studied this difference was even more dramatic with 46% of WS children versus 6% of control children classified as hypertensive (P = 0.01). We also demonstrated normal diurnal BP variation but no evidence of a "white coat" effect or increased BP variability. Interestingly, parental reporting of a history of infantile hypercalcemia was strongly associated with the presence of hypertension (P = 0.008). Our data demonstrate that both children and adults with WS have higher mean BP and higher frequency of hypertension than healthy controls. Thus, elevated BP readings in the office setting should not be dismissed but require more thorough assessment.

Identification and characterization of a highly conserved protein absent in the Alport syndrome (A), mental retardation (M), midface hypoplasia (M), and elliptocytosis (E) contiguous gene deletion syndrome (AMME)

We recently described a novel contiguous gene deletion syndrome (AMME) in Xq22.3 that includes Alport syndrome (A), mental retardation (M), midface hypoplasia (M), and elliptocytosis (E). While the Alport syndrome is due to deletion of the COL4A5 gene, no other genes are known in the region with the exception of our recent finding of the FACL4 gene. In our effort to isolate additional genes from the deleted region, we have identified the gene named AMMECR1 (Alport syndrome, mental retardation, midface hypoplasia, and elliptocytosis chromosomal region gene 1). RACE experiments and screening of cDNA libraries enabled us to obtain the entire ORF of the gene (1002 bp) followed by about 2 kb of 3'UTR. AMMECR1 is composed of six exons, shows a ubiquitous 6.5-kb transcript, and codes for a protein with a molecular mass of 35.5 kDa. Sequence analysis revealed that this gene is conserved in several species ranging from Caenorhabditis elegans and yeast to micro-organisms. Exon 2 of AMMECR1 encodes a domain consisting of six amino acids identically conserved throughout the course of evolution and whose function is as yet unknown. Analysis of the predicted protein product using ExPAsy tools raises the possibility that the gene may code for a regulatory factor potentially involved in the development of AMME contiguous gene deletion syndrome.

Identification of genes from a 500-kb region at 7q11.23 that is commonly deleted in Williams syndrome patients

Williams syndrome (WS) is a multisystem developmental disorder caused by the deletion of contiguous genes at 7q11.23. Hemizygosity of the elastin (ELN) gene can account for the vascular and connective tissue abnormalities observed in WS patients, but the genes that contribute to features such as infantile hypercalcemia, dysmorphic facies, and mental retardation remain to be identified. In addition, the size of the genomic interval commonly deleted in WS patients has not been established. In this study we report the characterization of a 500-kb region that was determined to be deleted in our collection of WS patients. A detailed physical map consisting of cosmid, P1 artificial chromosomes, and yeast artificial chromosomes was constructed and used for gene isolation experiments. Using the techniques of direct cDNA selection and genomic DNA sequencing, three known genes (ELN, LIMK1, and RFC2), a novel gene (WSCR1) with homology to RNA-binding proteins, a gene with homology to restin, and four other putative transcription units were identified. LIMK1 is a protein kinase with two repeats of the LIM/double zinc finger motif, and it is highly expressed in brain. RFC2 is the 40-kDa ATP-binding subunit of replication factor C, which is known to play a role in the elongation of DNA catalyzed by DNA polymerase delta and epsilon. LIMK1 and WSCR1 may be particularly relevant when explaining cognitive defects observed in WS patients.

A de novo satellited short arm of the Y chromosome possibly resulting from an unstable translocation

A satellited long arm of the Y chromosome (Yqs) is considered a normal variation, whereas the presence of a satellite on the short arm of the Y (Yps) has never been described in the literature. A Yps chromosome could be clinically significant if the translocation resulting in Yps has relocated the testis-determining gene, SRY, to another chromosome. A carrier of such a translocation would therefore be at increased risk for having XX male and XY female offspring. Here we describe the first reported case of de novo Yps present in a phenotypically normal male. This Yps chromosome was positive for C-banding and nucleolus organizer region (NOR) staining and showed a hybridization signal for the beta-satellite sequence. Fluorescence in situ hybridization (FISH) analysis indicated that SRY was retained on the Yps and the translocation breakpoint on Yps was distal to the pseudoautosomal region. At prenatal diagnosis, a normal appearing Y chromosome was found in his son, and thus the satellite on Yps was lost during meiotic Xp-Yp pairing. This Yps chromosome was likely the product of an "unstable" translocation.

Williams syndrome--oral presentation of 45 cases

Forty-five patients with Williams syndrome (WS) were evaluated for oral abnormalities. The mean age of the patients was 9.25 years, the median age was 6.7 years, and the majority (62.2%) were male. Hypodontia was present in 11.1% of the patients. Abnormal tooth morphology was noted in 12.5% of the primary dentitions and 40.7% of the permanent dentitions. With the exception of the primary mandibular central incisors of males, all mesiodistal incisor crown dimensions were statistically significantly smaller when compared with norms (P < 0.05). At least one hypoplastic enamel defect was present in 9.4% of patients with primary teeth and in 18.5% with permanent teeth. No patients exhibited generalized enamel hypoplasia. More than half of the patients (59.1%) were both caries and restoration free, while only 13.6% presented with clinically active caries. Tongue thrusting was present in 67.7% of the sample, while more than 50% of the patients present with excessive interdental spacing. Patients exhibited a higher than normal prevalence of Class II and III occlusions, open and deep bites and anterior crossbites. No single dental finding was pathognomonic of WS, however two constellations of findings, each occurring in approximately one-third of the sample, were observed: 1) microdontia, anterior crossbite, tongue thrusting, and excessive interdental spacing, and 2) microdontia, deep or open bite, and excessive interdental spacing.

Phenotypic heterogeneity of spinal muscular atrophy mapping to chromosome 5q11.2-13.3 (SMA 5q)

We made phenotypic analysis of 14 families with spinal muscular atrophy (SMA) linking to chromosome 5q11.2-13.3 (SMA 5q), and 2 that may not map to this locus, to assess clinical symptoms among SMA families known to result from mutation at the identical gene/locus. Although the current number of families is still small, the correlation of clinical phenotype and molecular genotype supports 2 observations. First, SMA mutations at the 5q locus present with a broad continuum of clinical abnormalities, and 2nd, the single clearly unlinked family presents with an unusual phenotype characterized by relatively late onset and early death. Thus, there are as yet no unambiguous cases of typical SMA families that are clearly unlinked to the locus at 5q-ie, no clear cases of nonallelic heterogeneity. Analysis of SMA 5q families supports the view that, with certain exceptions, there is little phenotypic intrafamilial variability. When families were ranked by severity of disease there was a strong correlation with age of onset. Onset within the 1st few months was associated with early death, but not in all cases. With rare exception, onset after 1 year of age was associated with less severe disease and greater longevity.