A linkage map of the Asian tiger mosquito (Aedes albopictus) based on cDNA markers.

The Asian tiger mosquito, Aedes (Stegomyia) albopictus (Skuse), is an important vector of a number of arboviruses, and populations exhibit extreme variation in adaptive traits such as egg diapause, cold hardiness, and autogeny (ability to mature a batch of eggs without blood feeding). The genetic basis of some of these traits has been established, but lack of a high-resolution linkage map has prevented in-depth genetic analyses of the genes underlying these complex traits. We report here on the breeding of 4 F(1) intercross mapping families and the use of these to locate 35 cDNA markers to the A. albopictus linkage map. The present study increases the number of markers on the A. albopictus cDNA linkage map from 38 to 73 and the density of markers from 1 marker/5.7 cM to 1 marker/2.9 cM and adds 9, 16, and 10 markers to the 3 linkage groups, respectively. The overall lengths of the 3 linkage groups are 64.5, 76.5, and 71.6 cM, respectively, for a combined length of 212.6 cM. Despite conservation in the order of most genes among the 4 families and a previous mapping family, we found substantial heterogeneity in the amount of recombination among markers. This was most marked in linkage group I, which varied between 16.7 and 69.3 cM. A map integrating the results from these 4 families with an earlier cDNA linkage map is presented.

Split medulla in association with multiple closed neural tube defects.

PURPOSE: We describe the case of a patient with a split medulla associated with multiple closed neural tube defects. CASE REPORT: This 13-year-old female initially presented to our service at just over a year of age for neck abnormalities and a congenital midline occipital dermal sinus. MRI and CT scans showed the presence of multiple cervical vertebral segmentation abnormalities, a bony spur at the level of the craniocervical junction, split medulla, split cervical spinal cord, and a midline occipital dermal sinus. Since the patient's neurological course had remained stable during follow-up for over 11 years, the only surgical procedure undertaken was excision of the dermal sinus to prevent infection. CONCLUSIONS: The constellation of abnormalities indicates that the notochord was split early during gestation, both rostral and caudal to the cervicomedullary junction. Surgical intervention to treat the other malformations needs to be considered only if the patient develops a progressive neurological deficit.

Reproductive Incompatibility Involving Senegalese Aedes aegypti (L) Is Associated with Chromosome Rearrangements.

Aedes aegypti, the primary vector of dengue, yellow fever and Zika flaviviruses, consists of at least two subspecies. Aedes aegypti (Aaa) is light in color, has pale scales on the first abdominal tergite, oviposits in artificial containers, and preferentially feeds on humans. Aedes aegypti formosus (Aaf), has a dark cuticle, is restricted to sub-Saharan Africa, has no pale scales on the first abdominal tergite and frequently oviposits in natural containers. Scale patterns correlate with cuticle color in East Africa but not in Senegal, West Africa where black cuticle mosquitoes display a continuum of scaling patterns and breed domestically indoors. An earlier laboratory study did not indicate any pre- or postzygotic barriers to gene flow between Aaa and Aaf in East Africa. However, similar attempts to construct F1 intercross families between Aaa laboratory strains and Senegal Ae. aegypti (SenAae) failed due to poor F1 oviposition and low F2 egg-to-adult survival. Insemination and assortative mating experiments failed to identify prezygotic mating barriers. Backcrosses were performed to test for postzygotic isolation patterns consistent with Haldane's rule modified for species, like Aedes, that have an autosomal sex determining locus (SDL). Egg-pupal survival was predicted to be low in females mated to hybrid F1 males but average when a male mates with a hybrid F1 female. Survival was in fact significantly reduced when females mated to hybrid males but egg-pupal survival was significantly increased when males were mated to hybrid F1 females. These observations are therefore inconclusive with regards to Haldane's rule. Basic cytogenetic analyses and Fluorescent In Situ Hybridization (FISH) experiments were performed to compare SenAae strains with the IB12 strain of Aaa that was used for genome sequencing and physical mapping. Some SenAae strains had longer chromosomes than IB12 and significantly different centromeric indices on chromosomes 1 and 3. DAPI staining was used to identify AT-rich regions, chromomycin A3 following pretreatment with barium hydroxide stained for GC-rich regions and stained the ribosomal RNA locus and YOYO-1 was used to test for differential staining. Chromosome patterns in SenAae strains revealed by these three stains differed from those in IB12. For FISH, 40 BAC clones previously physically mapped on Aaa chromosomes were used to test for chromosome rearrangements in SenAae relative to IB12. Differences in the order of markers identified two chromosomal rearrangements between IB12 and SenAae strains. The first rearrangement involves two overlapping pericentric (containing the centromere) inversions in chromosome 3 or an insertion of a large fragment into the 3q arm. The second rearrangement is close to the centromere on the p arm of chromosome 2. Linkage analysis of the SDL and the white-eye locus identified a likely chromosomal rearrangement on chromosome 1. The reproductive incompatibility observed within SenAae and between SenAae and Aaa may be generally associated with chromosome rearrangements on all three chromosomes and specifically caused by pericentric inversions on chromosomes 2 and 3.

Nondysraphic pediatric intramedullary spinal cord lipomas: report of 5 cases.

OBJECT: Intramedullary spinal cord lipomas not associated with dysraphism are infrequently reported. When present, they typically occur in children and have a predilection for the cervical and thoracic spinal cord. The authors review the presentation, treatment, and disease course in 5 pediatric patients, and compare the outcomes with previously reported cases. METHODS: With institutional review board approval, a retrospective chart review was undertaken at Children's Hospital Los Angeles. RESULTS: Four patients with intramedullary spinal cord lipomas and 1 patient with a lipoblastoma, none associated with dysraphism, were retrospectively reviewed. There were 2 boys and 3 girls ranging in age from 2 months to 4 years. Four patients underwent a laminectomy or laminoplasty with one or more subtotal resections. One patient initially underwent a decompressive laminoplasty without debulking. The median follow-up was 8 years (range 12 months-11 years). Two patients had regrowth of their lipoma, necessitating a second surgery in one patient and 3 debulking surgeries in the other. Postoperatively, 3 patients developed mild kyphosis, none significant enough to require orthopedic intervention. One patient underwent a stabilization procedure at the time of the initial laminectomy and tumor debulking. No patient received chemotherapy or radiation. At the most recent follow-up visit, patients demonstrated improved neurological function when compared with preoperative status. CONCLUSIONS: In addition to a decompressive laminectomy, debulking of the lipoma provides the best long-term neurological outcome. Gross-total excision is not warranted and usually is not possible. Long-term follow-up is needed, and repeat debulking of the lipoma is indicated if there is an increase in tumor size due to hyperplasia of residual adipocytes, when tumor growth is associated with neurological deterioration.