Frederick F. Elder

Cognitive and motor development during childhood in boys with Klinefelter syndrome.

The goal of this study was to expand the description of the cognitive development phenotype in boys with Klinefelter syndrome (47,XXY). We tested neuropsychological measures of memory, attention, visual‐spatial abilities, visual‐motor skills, and language. We examined the influence of age, handedness, genetic aspects (parental origin of the extra X chromosome, CAGn repeat length, and pattern of X inactivation), and previous testosterone treatment on cognition. We studied 50 boys with KS (4.1–17.8 years). There was a significant increase in left‐handedness (P = 0.002). Specific language, academic, attentional, and motor abilities tended to be impaired. In the language domain, there was relative sparing of vocabulary and meaningful language understanding abilities but impairment of higher level linguistic competence. KS boys demonstrated an array of motor difficulties, especially in strength and running speed. Deficits in the ability to sustain attention without impulsivity were present in the younger boys. Neither genetic factors examined nor previous testosterone treatment accounted for variation in the cognitive phenotype in KS. The cognitive results from this large KS cohort may be related to atypical brain lateralization and have important diagnostic and psychoeducational implications. The difficulty in complex language processing, impaired attention and motor function in boys with KS may be missed. It is critical that boys with KS are provided with appropriate educational support that targets their learning challenges in school in addition to modifications that address their particular learning style. These findings would also be an important component of counseling clinicians and families about this disorder.

Early androgen deficiency in infants and young boys with 47,XXY Klinefelter syndrome.

Background/Aims: Klinefelter syndrome (KS) is characterized by the karyotype 47,XXY. In this study, we evaluated the physical and testicular failure phenotypes of infants and young boys with KS. Methods: The evaluation included auxologic measurements, biologic indices of testicular function, and clinical assessment of muscle tone in 22 infants and young boys with KS, ages 1–23 months. Results: Mean length, weight, and head circumference in SDS were generally within the normal range at –0.3 ± 1.0, –0.1 ± 1.4, and 0.0 ± 1.5, respectively. Mean penile length and testicular volume SDS were –0.9 ± 0.8 and –1.1 ± 0.8, indicating significantly reduced penile and testicular size. Mean testosterone levels for the boys ≤6 and >6–23 months were 128 ± 131 (4.4 ± 4.5 nmol/l) and 9.5 ± 7.2 ng/dl (0.3 ± 0.2 nmol/l), respectively. High-arched palate was observed in 6/17 boys and clinodactyly (5th finger) was observed in 15/16 boys. Hypotonia was evaluated clinically and was noted to be present in 12/17 boys. Conclusion: The physical phenotype in infants and young boys with KS (1–23 months old) includes normal auxologic measurements and early evidence of testicular failure. Muscle tone was decreased in most of the boys. Testicular volume and penile length were diminished, indicating early androgen deficiency. The neonatal surge in testosterone was attenuated in our KS population. Thus, infants and young boys with KS have evidence of early testicular failure. The etiology of this failure and the clinical role of early androgen replacement require further study.

Cryptic Chromosomal Abnormalities Identified in Children With Congenital Heart Disease

Congenital heart disease (CHD) is the most common type of birth defect, and the etiology of most cases is unknown. CHD often occurs in association with other birth malformations, and only in a minority are disease-causing chromosomal abnormalities identified. We hypothesized that children with CHD and additional birth malformations have cryptic chromosomal abnormalities that might be uncovered using recently developed DNA microarray-based methodologies. We recruited 20 children with diverse forms of CHD and additional birth defects who had no chromosomal abnormality identified by conventional cytogenetic testing. Using whole-genome array comparative genomic hybridization, we screened this population, along with a matched control population with isolated heart defects, for chromosomal copy number variations. We discovered disease-causing cryptic chromosomal abnormalities in five children with CHD and additional birth defects versus none with isolated CHD. The chromosomal abnormalities included three unbalanced translocations, one interstitial duplication, and one interstitial deletion. The genetic abnormalities were predominantly identified in children with CHD and a neurologic abnormality. Our results suggest that a significant percentage of children with CHD and neurologic abnormalities harbor subtle chromosomal abnormalities. We propose that children who meet these two criteria should receive more extensive genetic testing to detect potential cryptic chromosomal abnormalities.

A turner syndrome neurocognitive phenotype maps to Xp22.3

BackgroundTurner syndrome (TS) is associated with a neurocognitive phenotype that includes selective nonverbal deficits, e.g., impaired visual-spatial abilities. We previously reported evidence that this phenotype results from haploinsufficiency of one or more genes on distal Xp. This inference was based on genotype/phenotype comparisons of individual girls and women with partial Xp deletions, with the neurocognitive phenotype considered a dichotomous trait. We sought to confirm our findings in a large cohort (n = 47) of adult women with partial deletions of Xp or Xq, enriched for subjects with distal Xp deletions.MethodsSubjects were recruited from North American genetics and endocrinology clinics. Phenotype assessment included measures of stature, ovarian function, and detailed neurocognitive testing. The neurocognitive phenotype was measured as a quantitative trait, the Turner Syndrome Cognitive Summary (TSCS) score, derived from discriminant function analysis. Genetic analysis included karyotyping, X inactivation studies, fluorescent in situ hybridization, microsatellite marker genotyping, and array comparative genomic hybridization.ResultsWe report statistical evidence that deletion of Xp22.3, an interval containing 31 annotated genes, is sufficient to cause the neurocognitive phenotype described by the TSCS score. Two other cardinal TS features, ovarian failure and short stature, as well as X chromosome inactivation pattern and subjects age, were unrelated to the TSCS score.ConclusionDetailed mapping suggests that haploinsufficiency of one or more genes in Xp22.3, the distal 8.3 megabases (Mb) of the X chromosome, is responsible for a TS neurocognitive phenotype. This interval includes the 2.6 Mb Xp-Yp pseudoautosomal region (PAR1). Haploinsufficiency of the short stature gene SHOX in PAR1 probably does not cause this TS neurocognitive phenotype. Two genes proximal to PAR1 within the 8.3 Mb critical region, STS and NLGN4X, are attractive candidates for this neurocognitive phenotype.

Lagomorphs (rabbits, pikas and hares) do not use telomere-directed replicative aging in vitro

Telomere shortening is used for replicative aging in primates and ungulates but not rodents. We examined telomere biology in rabbits to expand the comparative biology of telomere-directed replicative senescence within mammals. The order Lagomorpha consists of two families; Leporidae and Ochotonidae. We examined telomere biology in species representing three leporid genera (European White Rabbit, Black-tailed Jack Rabbit, and Swamp Rabbit) and the monotypic ochotonid genus (North American Pika). Of the leporids one species was a laboratory strain and the others were wild caught. The leporids neither exhibited cellular senescence after sustained periods in culture nor displayed detectable telomerase activity. Continued culture was possible because of their extremely long telomeric arrays. Immunofluorescence showed robust telomere signals at chromosome ends and significant internal chromosomal staining in some instances. Pika was unique in displaying endogenous telomerase activity throughout time in culture. These results show that it is unlikely that lagomorphs use telomere shortening and replicative senescence as a tumor protective mechanism.

Differences in activity and phosphorylation of MAPK enzymes in esophageal squamous cells of GERD patients with and without Barrett's esophagus

We hypothesized that, in esophageal squamous epithelial cells, there are differences among individuals in the signal transduction pathways activated by acid reflux that might underlie the development of Barretts esophagus. To explore that hypothesis, we immortalized nonneoplastic, esophageal squamous cells from patients with gastroesophageal reflux disease (GERD) with (NES-B3T) and without (NES-G2T) Barretts esophagus and used those cells to study acid effects on MAPK proteins. During endoscopy in patients with GERD with and without Barretts esophagus, we took biopsy specimens from the distal squamous esophagus to study MAPK proteins before and after esophageal perfusion with 0.1 N HCl. We used immunoblotting and Western blotting to study MEK1/2 phosphorylation at two activating sites (serines 217/221), MEK1 phosphorylation at an inhibitory site (threonine 286), and MEK1/2 activity. After acid exposure, both cell lines exhibited increased MEK1/2 phosphorylation at the activating sites; the NES-B3T cells had higher levels of MEK1 phosphorylation at the inhibitory site, however, and only the NES-G2T cells showed an acid-induced increase in MEK1/2 activity. Similarly, in the squamous epithelium of patients with GERD with and without Barretts esophagus, acid perfusion increased MEK1/2 phosphorylation at the activating sites in both patient groups; the Barretts patients had higher levels of MEK1 phosphorylation at the inhibitory site, however, and only the patients without Barretts demonstrated an acid-induced increase in ERK1/2 phosphorylation. In esophageal squamous cell lines and biopsies from patients with GERD with and without Barretts esophagus, we have found differences in MAPK pathways activated by acid exposure. We speculate that these differences might underlie the development of Barretts metaplasia.

Genetic mapping of an insertional hydrocephalus-inducing mutation allelic to hy3

The transgenic mouse line OVE459 carries a transgene-induced insertional mutation resulting in autosomal recessive congenital hydrocephalus. Homozygous transgenic animals experience ventricular dilation with perinatal onset and are noticeably smaller than hemizygous or non-transgenic littermates within a few days after birth. Fluorescence in situ hybridization (FISH) revealed that the transgene inserted in a single locus on mouse Chromosome (chr) 8, region D2-E1. Genetic crosses between hemizygous OVE459 mice and mice heterozygous for the spontaneous mutation hydrocephalus-3 (hy3) produced hydrocephalic offspring with a frequency of 22%, demonstrating that these two mutations are allelic. A genomic library was made by using DNA from homozygous OVE459 mice, and genomic DNA flanking the transgene insertion site was isolated and sequenced. A PCR polymorphism between C57BL/6 DNA and Mus spretus was used to map the location of the transgene insert to 1.06 cM ± 0.75 proximal to D8Mit152 by using the Jackson Laboratory Backcross DNA Panel Mapping Resource. Furthermore, sequence analysis from a mouse bacterial artificial chromosome (BAC) clone, positive for unique markers on both sides of the transgene insertion site, demonstrated that the genomic DNAs flanking each side of the transgene insertion are physically separated by approximately 51 kb on the wild-type mouse chromosome.

A man who inherited his SRY gene and Leri-Weill dyschondrosteosis from his mother and neurofibromatosis type 1 from his father

We report on a man with neurofibromatosis type 1 (NF1) and Leri-Weill dyschondrosteosis (LWD). His father had NF1. His mother had LWD plus additional findings of Turner syndrome (TS): high arched palate, bicuspid aortic valve, aortic stenosis, and premature ovarian failure. The probands karyotype was 46,X,dic(X;Y)(p22.3;p11.32). Despite having almost the same genetic constitution as 47,XXY Klinefelter syndrome, he was normally virilized, although slight elevation of serum gonadotropins indicated gonadal dysfunction. His mothers karyotype was mosaic 45,X[17 cells]/46,X,dic(X;Y)(p22.3;p11.32)[3 cells].ish dic(X;Y)(DXZ1 +,DYZ1 + ). The dic(X;Y) chromosome was also positive for Y markers PABY, SRY, and DYZ5, but negative for SHOX. The dic(X;Y) chromosome was also positive for X markers DXZ1 and a sequence < 300 kb from PABX, suggesting that the deletion encompassed only pseudoautosomal sequences. Replication studies indicated that the normal X and the dic(X;Y) were randomly inactivated in the probands lymphocytes. LWD in the proband and his mother was explained by SHOX haploinsufficiency. The mothers female phenotype was most likely due to 45,X mosaicism. This family segregating Mendelian and chromosomal disorders illustrates extreme sex chromosome variation compatible with normal male and female sexual differentiation. The case also highlights the importance of karyotyping for differentiating LWD and TS, especially in patients with findings such as premature ovarian failure or aortic abnormalities not associated with isolated SHOX haploinsufficiency.

Complete trisomy 1q with mosaic Y;1 translocation: A recurrent aneuploidy presenting diagnostic dilemmas

We present a case of a liveborn male with complete trisomy 1q in mosaic form due to a de novo unbalanced translocation. There are seven previously documented cases of complete trisomy for 1q, which demonstrate that this is a lethal condition. All cases have similar phenotype including weights greater than 50th centile for gestational age, hydrocephalus, microphthalmia, abnormal ears, small mouth or jaw, and abnormal fingers. Single umbilical artery, imperforate anus, and dysplastic kidneys are also seen in more than one patient. Five of the eight translocation cases have identical chromosomal breakpoints involving 1q and Yq. This suggests the possibility of sequence similarities on these two chromosomes as has been documented with several other recurrent chromosomal rearrangements. Further, this case demonstrates the need for postnatal genetics evaluation following prenatal diagnosis. In postnatal testing, the aneuploidy could not be demonstrated in metaphase cells from cultured lymphocytes. More detailed testing prompted by abnormal amniocentesis and neonatal dysmorphology was necessary to confirm the cytogenetic diagnosis. Without the prenatal diagnosis, it is likely that the true cytogenetic aberration would have gone undetected.

exma: an X-linked insertional mutation that disrupts forebrain and eye development.

Abstract. Formation of the neural tube plays a primary role in establishing the body plan of the vertebrate embryo. Here we describe the phenotype and physical mapping of a highly penetrant X-linked male-lethal murine mutation, exma (exencephaly, microphthalmia/anophthalmia), that specifically disrupts development of the rostral neural tube and eye. The mutation arose from the random insertion of a transgene into the mouse X Chromosome (Chr). Eighty-three percent of transgenic male embryos display an open, disorganized forebrain and lack optic vesicles. No transgenic males survive beyond birth. Hemizygous females show a variable phenotype, including reduced viability and occasional exencephaly and/or microphthalmia. Altered or reduced expression patterns of Otx2, Pax6, Six3, and Mrx, known markers of early forebrain and eye development, confirmed the highly disorganized structure of the forebrain and lack of eye development in affected exma male embryos. Physical mapping of the transgene by FISH localized a single insertion site to the interval between Dmd and Zfx on the X Chr. A 1-Mb contig of BAC clones was assembled by using sequences flanking the transgene and revealed that the insertion lies close to Pola1 and Arx, a gene encoding a highly conserved homeobox protein known to be expressed in the developing forebrain of the mouse. Data from Southern blots of normal and transgenic DNA demonstrated that a large segment of DNA encompassing Arx and including part of Pola1 was duplicated as a result of the transgene insertion. From the physical mapping results, we propose a model of the gross rearrangements that accompanied transgene integration and discuss its implications for evaluating candidate genes for exma.