DNA microarray analysis identifies candidate regions and genes in unexplained mental retardation.

OBJECTIVE: Because in most patients with mental retardation (MR), who constitute 2 to 3% of the population, the etiology remains unknown, we wanted to identify novel chromosomal candidate regions and genes associated with the MR phenotype. METHODS: We screened for microimbalances in 60 clinically well-characterized patients with unexplained MR mostly combined with congenital anomalies. Genome-wide array-based comparative genomic hybridization was performed on DNA microarrays with an average resolution of <0.5 Mb. We verified every nonpolymorphic array clone outside the diagnostic thresholds by fluorescence in situ hybridization and performed breakpoint analyses on confirmed imbalances. RESULTS: Six presumably causal microimbalances were detected, five of which have not been reported. Microdeletions were found in five patients with MR and distinctive facial features, who also had neurologic findings (three cases), brain anomalies (two cases), and growth retardation (two cases), in chromosomal bands 6q11.1-q13 (10.8 Mb), Xq21.31-q21.33 (4.0 Mb), 1q24.1-q24.2 (3.8 Mb), 19p13.12 (2.1 Mb), and 4p12-p13 (1.1 Mb). One microduplication was detected in 22q11.2 (2.8 Mb) including the DiGeorge syndrome critical region in a patient with mild MR, microcephaly at birth, and dysmorphisms. Three imbalances were shown to be de novo and two inherited. The Xq21 microdeletion in a boy with borderline intellectual functioning was inherited from a normal mother; the 22q11.2 microduplication was inherited from a normal father and was present in two affected siblings. CONCLUSION: We could identify novel microimbalances as the probable cause of mental retardation in 10% of patients with unclear etiology. The gene content of the microimbalances was found to correlate with phenotype severity. Precise breakpoint analyses allowed the identification of deleted genes presumably causing mental retardation.

Role of actin depolymerization in the surfactant secretory response of alveolar epithelial type II cells.

Alveolar epithelial type II cells (AET2) respond with exocytosis of surfactant containing lamellar bodies to stimulation with mechanical stretch and secretagogues, a process that is fundamental for maintaining alveolar stability and lung gas exchange. In the present study in cultured rat AET2, we employed botulinum C2 toxin, a binary toxin which ADP ribosylates nonmuscle G-actin, as a specific tool to probe the role of the actin microfilament system in the surfactant secretory process. Incubation of AET2 with C2 toxin caused a dose-dependent decay of the cellular F-actin content to a minimum of 20% of baseline, concomitant with an increase in monomeric actin. In parallel, a significant augmentation of baseline surfactant secretion up to twofold elevated levels above control was noted, as assessed by the release of prelabeled phosphatidylcholine. Pretreatment with phalloidin, which stabilized F-actin and reduced the level of G-actin, prevented the C2 toxin-elicited enhancement of baseline surfactant secretion. Even low C2 toxin concentrations, resulting in a reduction of total cellular F-actin content of approximately 10%, sufficed to augment secretagogue (ATP) and, more impressively, mechanical stress elicited an increase in surfactant secretion; the response to the biophysical challenge more than doubled. When investigated in the absence of toxin, different secretagogues (ATP, phorbol ester, betamimetics) caused a rapid-onset, transient reduction of F-actin in the range between 15 and 25% as a consistent part of their secretory response pattern. These data suggest that the state of actin polymerization is intimately linked to the exocytosis process underlying surfactant secretion in AET2. Microfilament system-related compartmentalization effects and/or or the impact of the state of actin assembly on signaling events may be considered as underlying events.

Cervicography combined with repeat Papanicolaou test as triage for low-grade cytologic abnormalities.

OBJECTIVE: To determine the efficacy of combined repeat Papanicolaou test and cervicography for identification of high-grade squamous lesions among patients who previously have had atypical squamous cells of undetermined significance (ASCUS) or low-grade squamous intraepithelial lesion (LSIL) diagnosed by the Bethesda System. METHODS: All patients who presented to a charity hospital gynecology clinic between July 1, 1994, and December 31, 1995, with a Papanicolaou test result of ASCUS or LSIL underwent repeat Papanicolaou test, cervicography, colposcopy with colposcopic-directed biopsy when appropriate, and an endocervical curettage. Pregnant patients and those who had undergone hysterectomy were excluded. The mean and median time from abnormal Papanicolaou test to clinical investigation was 61 and 58 days, respectively (range 6-162 days). RESULTS: One hundred eighty-seven of the patients had an initial ASCUS Papanicolaou test. Of these 187, 24 (13%) were found to have cervical intraepithelial neoplasia (CIN) grades II-III. The second Papanicolaou test would have resulted in the detection of 11 of 24 lesions (sensitivity 46%), whereas the cervigram would have detected 22 of 24 (sensitivity 92%). The combined Papanicolaou test and cervigram sensitivity for ASCUS was 91%. One hundred forty-one of the patients had an initial LSIL Papanicolaou test. Of these 141, 37 (26%) patients were found to have CIN II-III. The repeat Papanicolaou test would have detected 29 of 37 lesions (sensitivity 78%), whereas the cervigram would have detected 33 of 37 (sensitivity 89%). The combined Papanicolaou test and cervigram sensitivity for LSIL was 97%. CONCLUSION: Cervicography is a helpful adjunctive technique for detection of CIN II-III lesions in patients with previous ASCUS or LSIL Papanicolaou tests.