Phenotype analysis impacts testing strategy in patients with Currarino syndrome.

Currarino syndrome (OMIM 175450) presents with sacral, anorectal, and intraspinal anomalies and presacral meningocele or teratoma. Autosomal dominant loss-of-function mutations in the MNX1 gene cause nearly all familial and 30% of sporadic cases. Less frequently, a complex phenotype of Currarino syndrome can be caused by microdeletions of 7q containing MNX1. Here, we report one familial and three sporadic cases of Currarino syndrome. To determine the most efficient genetic testing approach for these patients, we have compared results from MNX1 sequencing, chromosomal microarray, and performed a literature search with analysis of genotype-phenotype correlation. Based on the relationship between the type of mutation (intragenic MNX1 mutations vs 7q microdeletion) and the presence of intellectual disability, growth retardation, facial dysmorphism, and associated malformations, we propose a testing algorithm. Patients with the classic Currarino triad of malformations but normal growth, intellect, and facial appearance should have MNX1 sequencing first, and only in the event of a normal result should the clinician proceed with chromosomal microarray testing. In contrast, if growth delay and/or facial dysmorphy and/or intellectual disability are present, chromosomal microarray should be the first method of choice for genetic testing.

Further Evidence of Contrasting Phenotypes Caused by Reciprocal Deletions and Duplications: Duplication of NSD1 Causes Growth Retardation and Microcephaly.

Microduplications of the Sotos syndrome region containing NSD1 on 5q35 have recently been proposed to cause a syndrome of microcephaly, short stature and developmental delay. To further characterize this emerging syndrome, we report the clinical details of 12 individuals from 8 families found to have interstitial duplications involving NSD1, ranging in size from 370 kb to 3.7 Mb. All individuals are microcephalic, and height and childhood weight range from below average to severely restricted. Mild-to-moderate learning disabilities and/or developmental delay are present in all individuals, including carrier family members of probands; dysmorphic features and digital anomalies are present in a majority. Craniosynostosis is present in the individual with the largest duplication, though the duplication does not include MSX2, mutations of which can cause craniosynostosis, on 5q35.2. A comparison of the smallest duplication in our cohort that includes the entire NSD1 gene to the individual with the largest duplication that only partially overlaps NSD1 suggests that whole-gene duplication of NSD1 in and of itself may be sufficient to cause the abnormal growth parameters seen in these patients. NSD1 duplications may therefore be added to a growing list of copy number variations for which deletion and duplication of specific genes have contrasting effects on body development.

PHOG, a candidate gene for involvement in the short stature of Turner syndrome.

The abnormalities seen in Turner syndrome (monosomy X) presumably result from haploinsufficiency of certain genes on the X chromosome. Gene dosage considerations lead to the prediction that the culpable genes escape X inactivation and have functional homologs on the Y chromosome. Among the genes with these characteristics are those residing in the pseudoautosomal regions (PAR) of the sex chromosomes. A pseudoautosomal location for a dosage-sensitive locus involved in stature has been suggested based on the analyses of patients with deletions of a specific segment of the short arm PAR; hemizygosity for this putative locus probably also contributes to the short stature in Turner individuals. We have isolated a gene from the critical deleted region that encodes a novel homeodomain-containing transcription factor and is expressed at highest levels in osteogenic cells. We have named the gene PHOG, for pseudoautosomal homeobox-containing osteogenic gene. Its deletion in patients with short stature, the predicted altered dosage in 45,X individuals, along with the nature of the encoded protein and its expression pattern, make PHOG an attractive candidate for involvement in the short stature of Turner syndrome. We have also found that the mouse homolog of PHOG is autosomal, which may help to explain the lack of a growth abnormality in mice with monosomy X.

Featural evaluation, integration, and judgment of facial affect.

The paradigm of the fuzzy logical model of perception (FLMP) is extended to the domain of perception and recognition of facial affect. Two experiments were performed using a highly realistic computer-generated face varying on 2 features of facial affect. Each experiment used the same expanded factorial design, with 5 levels of brow deflection crossed with 5 levels of mouth deflection, as well as their corresponding half-face conditions, for a total stimulus set of 35 faces. Experiment 1 used a 2-alternative, forced-choice paradigm (either happy or angry), whereas Experiment 2 used 9 rating steps from happy to angry. Results indicate that participants evaluated and integrated information from both features to perceive affective expressions. Both choice probabilities and ratings showed that the influence of 1 feature was greater to the extent that the other feature was ambiguous. The FLMP fit the judgments from both experiments significantly better than an additive model. Our results question previous claims of categorical and holistic perception of affect.

Perceptual recognition of facial affect: cross-cultural comparisons.

Previous research has shown that the perception of affect in faces is well described by the fuzzy logical model of perception (FLMP). In this study, we asked whether the processes involved in recognition depended on the race/culture of the face and/or of the perceiver. A computer-generated face was used to manipulate two features of facial affect: brow deflection and mouth deflection. An expanded-factorial design was used, with four levels of brow deflection crossed with four levels of mouth deflection, as well as their corresponding half-face conditions. Participants identified these faces as either happy or angry. Japanese and U.S. students were tested on faces from these two countries that were texture-mapped onto the animated face. The FLMP gave the best description of performance for both groups and for both types of faces. These findings challenge previous claims of holistic perception, categorical perception, and additive feature integration.

Genetic mapping of the adenine nucleotide translocase-2 gene (Ant2) to the mouse proximal X chromosome.

Adenine nucleotide translocases are mitochondrial membrane proteins encoded by a small dispersed multigene family. We have previously cloned cDNAs derived from the mouse adenine nucleotide translocase-1 and -2 genes (Ant1 and Ant2) and assigned the loci to mouse chromosomes 8 and X, respectively. Here we describe the genomic organization of the Ant2 gene and its regional map position on the X chromosome, which was determined through linkage analysis using an interspecific backcross between Mus musculus and Mus spretus inbred strains. Ant2 cosegregates with DXMit49 and DXMit50 and lies distal to Agtr2 in the proximal region of the mouse X chromosome. This map assignment further defines a region of conserved synteny between human Xq22-q25 and the mouse proximal X chromosome.

Rapid evolution of human pseudoautosomal genes and their mouse homologs.

Comparative studies of genes in the pseudoautosomal region (PAR) of human and mouse sex chromosomes have thus far been very limited. The only comparisons that can presently be made indicate that the PARs of humans and mice are not identical in terms of gene content. Here we describe additional comparative studies of human pseudoautosomal genes and their mouse homologs. Using a somatic cell hybrid mapping panel, we have assigned the mouse homolog of the human pseudoautosomal interleukin 3 receptor alpha subunit (IL3RA) gene to mouse Chromosome (Chr) 14. Attempts to clone the mouse homolog of the human pseudoautosomal adenine nucleotide translocase-3 (ANT3) gene resulted in the isolation of the murine homologs of the human ANT1 and ANT2 genes. The mouse Ant1 and Ant2 genes are very similar in sequence to their human homologs, and we have mapped them to mouse Chromosomes (Chrs) (8 and X respectively) that exhibit conserved synteny with the chromosomes on which the human genes are located. In contrast, the homolog of ANT3 appears to be either very divergent or absent from the mouse genome. Southern blot analysis of DNA from a variety of mammalian species shows restricted conservation of human pseudoautosomal genes, a trend that also applies to the two cloned mouse homologs of these genes and to neighboring human genes in distal Xp22.3. Our observations combined with those of other workers lead us to propose a model for the evolution of the PAR that includes both rapid sequence evolution and the incremental reduction in size of the region during mammalian evolution.

Characterization of a YAC contig spanning the pseudoautosomal region.

Due to its unique biology of partial sex linkage and high recombination rates, the pseudoautosomal region (PAR1) on both X and Y chromosomes has attracted considerable interest. In addition, an extremely high level of YAC instability has been observed in this region. We have derived 82 YAC clones from six different YAC libraries mapping to this 2.6-Mb region. Of these a subset of 22 YACs was analyzed in detail. YAC contigs were assembled using 67 pseudoautosomal probes, of which 64 were unambiguously ordered. All markers are well distributed over the entire region, including the middle part of the region, which has previously been found difficult to contig. Two gaps of less than 50 kb within the genomic locus of CSF2RA and around XE7 remain, which could not be covered with YACs, cosmids, or phages. This YAC contig anchored on the physical map of PAR1 represents one of the best characterized large regions of the human genome with a map completion greater than 90% at 100-kb resolution and has permitted the accurate localization of all known genes within this region.

Structure and expression of the human pseudoautosomal gene XE7.

The human pseudoautosomal region comprises a 2.6 megabase segment of the distal short arms of the X and Y chromosomes. Complete DNA sequence homology between the two sex chromosomes is found in this region, and is believed to be important in mediating X-Y pairing in male meiosis. The only known functional genes in this region are MIC2 and CSF2R; in addition a pseudoautosomal location has been proposed for a genetic locus controlling stature. Here we report the structure of a recently identified pseudoautosomal gene, XE7, and its expression in human tissues. Analysis of genomic and cDNA clones shows that alternative RNA splicing results in the production of two predicted protein isoforms, one containing 385 amino acids and the other with 695 residues. The smaller polypeptide is a truncated version of the larger, and results from the inclusion of a cassette exon that introduces an in-frame stop codon into the mRNA. The XE7 gene appears to be ubiquitously expressed, and the production of both protein isoforms is predicted in each of several tissues examined.

Regulation of cytoplasmic mRNA prevalence in sea urchin embryos. Rates of appearance and turnover for specific sequences.

Complementary DNA clones representing cytoplasmic poly(A) RNAs of sea urchin embryos were hybridized with metabolically labeled cytoplasmic RNA preparations and the rates of appearance and of decay for each transcript species were determined at the blastula-gastrula stage of development. The prevalence of the transcripts chosen for this study ranged, on average, from about one molecule per cell to a few hundred molecules per cell. The embryos were labeled continuously for 18 hours with [3H]guanosine, beginning at 24 hours post-fertilization. The amount of cytoplasmic [3H]poly(A) RNA that hybridized to each cloned sequence was determined and the specific activity of the [3H]GTP pool was measured in the same embryos. Rate constants for the entry of each transcript species into the cytoplasm, and for its decay were extracted from these data. The embryo transcript species identified by the cloned probes displayed a range of stabilities. Half-lives of only a few hours were measured both for a very rare sequence and for a moderately prevalent sequence. Other newly synthesized transcripts, including sequences that first appear during embryonic development, as well as sequences also represented in maternal RNA, are far more stable. We conclude that cytoplasmic RNA turnover rate is a major variable in the determination of the cytoplasmic level of expression of embryo genes. The entry rates of the transcripts into the cytoplasm also varied, from a few molecules per embryo per minute to several hundred, depending on the sequence. By comparing the mass of transcripts of a given sequence in the embryo to the mass of transcripts of that sequence accumulating as a result of new synthesis, the point at which embryo transcription accounts for the major fraction of the cytoplasmic molecules could be estimated. This calculation showed that for some sequences maternal transcripts persist well beyond gastrulation, while other embryo poly(A) RNA species are largely the product of transcription in the embryo nuclei from the blastula stage onwards. There is no single stage at which all maternal transcripts are suddenly replaced by newly synthesized embryo transcripts. Primary transcription rates were measured for two sequences by determining accumulation of label in these RNA species soon after addition of [3H]guanosine to the cultures. Comparing these rates to the cytoplasmic entry rates, we did not detect a significantly greater nuclear transcription of the sequence homologous to the cloned probe.

The nucleotide sequence of a human immunoglobulin C gamma1 gene.

We report the nucleotide sequence of a gene encoding the constant region of a human immunoglobulin gamma 1 heavy chain (C gamma 1). A comparison of this sequence with those of the C gamma 2 and C gamma 4 genes reveals that these three human C gamma genes share considerable homology in both coding and noncoding regions. The nucleotide sequence differences indicate that these genes diverged from one another approximately 608 million years ago. An examination of hinge exons shows that these coding regions have evolved more rapidly than any other areas of the C gamma genes in terms of both base substitution and deletion/insertion events. Coding sequence diversity also is observed in areas of CH domains which border the hinge.