Laser Epilation as an Adjunct to Standard Care in Reducing Pilonidal Disease Recurrence in Adolescents and Young Adults: A Randomized Clinical Trial

Importance

Recurrence continues to be a significant challenge in the treatment and management of pilonidal disease.

Objective

To compare the effectiveness of laser epilation (LE) as an adjunct to standard care vs standard care alone in preventing recurrence of pilonidal disease in adolescents and young adults.

Design, Setting, and Participants

This was a single-institution, randomized clinical trial with 1-year follow-up conducted from September 2017 to September 2022. Patients aged 11 to 21 years with pilonidal disease were recruited from a single tertiary children's hospital.

Intervention

LE and standard care (improved hygiene and mechanical or chemical depilation) or standard care alone.

Main Outcomes and Measures

The primary outcome was the rate of recurrence of pilonidal disease at 1 year. Secondary outcomes assessed during the 1-year follow-up included disability days, health-related quality of life (HRQOL), health care satisfaction, disease-related attitudes and perceived stigma, and rates of procedures, surgical excisions, and postoperative complications.

Results

A total of 302 participants (median [IQR] age, 17 [15-18] years; 157 male [56.1%]) with pilonidal disease were enrolled; 151 participants were randomly assigned to each intervention group. One-year follow-up was available for 96 patients (63.6%) in the LE group and 134 (88.7%) in the standard care group. The proportion of patients who experienced a recurrence within 1 year was significantly lower in the LE treatment arm than in the standard care arm (-23.2%; 95% CI, -33.2 to -13.1; P < .001). Over 1 year, there were no differences between groups in either patient or caregiver disability days, or patient- or caregiver-reported HRQOL, health care satisfaction, or perceived stigma at any time point. The LE group had significantly higher Child Attitude Toward Illness Scores (CATIS) at 6 months (median [IQR], 3.8 [3.4-4.2] vs 3.6 [3.2-4.1]; P = .01). There were no differences between groups in disease-related health care utilization, disease-related procedures, or postoperative complications.

Conclusions and Relevance

LE as an adjunct to standard care significantly reduced 1-year recurrence rates of pilonidal disease compared with standard care alone. These results provide further evidence that LE is safe and well tolerated in patients with pilonidal disease. LE should be considered a standard treatment modality for patients with pilonidal disease and should be available as an initial treatment option or adjunct treatment modality for all eligible patients.

Trial Registration

ClinicalTrials.gov Identifier: NCT03276065.

Sexual and reproductive health education for patients with myelomeningocele

AIM

To evaluate the sexual and reproductive health education received by patients with myelomeningocele, the most severe form of spina bifida.

METHOD

A survey designed to assess the sexual and reproductive health education given by a healthcare provider to patients with myelomeningocele was offered to all English-speaking patients aged 12 years or older with a myelomeningocele clinic visit.

RESULTS

In total, 67 surveys were completed. Menstruation and menstrual management were discussed at a rate of 85% in females. Few patients had discussions with a provider about fertility (42%), sexuality (37%), risk of sexually transmitted infections (45%), or had a relationship with a reproductive healthcare provider (54%). Differences by sex were observed for contraceptive education. The rate of discussions increased with age. A total of 67% of female patients and 33% of male patients requested a referral to a reproductive healthcare provider.

INTERPRETATION

Sexual and reproductive health education is part of comprehensive care for all patients and those with disabilities should not be excluded. The lack of consistent education received by patients supports the need for increased attention to this topic. We encourage multidisciplinary myelomeningocele clinics to establish a process for delivering complete and patient-specific sexual and reproductive health education.

Levonorgestrel-Releasing Intrauterine System Utilization in Patients with Developmental Delays

INTRODUCTION

Adolescent females with developmental delays (DDs) experience unique physical and emotional challenges related to menstruation. Providers often recommend hormonal medication for menstrual management. The objective of our study was to describe the utilization and safety of the levonorgestrel-releasing intrauterine system (LNG-IUS) in adolescents with DDs.

METHODS

We utilized the Pediatric Health Information System to identify females aged 10-25 with DDs who underwent an LNG-IUS insertion between 2011 and 2020. Using a gynecologic procedure and diagnosis codes, we assessed indications for and complications of LNG-IUS use. We also evaluated early LNG-IUS removal.

RESULTS

One thousand five hundred and sixty female patients with DDs underwent LNG-IUS insertion. LNG-IUS insertion under anesthesia was most commonly performed in patients with autism and Down syndrome, and unspecified menstrual issues were documented for 40% of the cohort. Perforation was observed in 11 patients (1%), and mechanical complications (malpositioned IUS or lost threads) were observed in 23 patients (1%).

DISCUSSION

This is the largest analysis of LNG-IUS use in patients with DDs to our knowledge and shows the utilization of LNG-IUS in patients with DDs. We provide descriptive information that providers can use to accurately advise their patients with DDs on the risks and benefits of LNG-IUS use for menstrual management.

Variability in the management of adhesive small bowel obstruction in children

BACKGROUND

This study assessed inter-hospital variability in operative-vs-nonoperative management of pediatric adhesive small bowel obstruction (ASBO).

METHODS

A multi-institutional retrospective study was performed examining patients 1-21 years-of-age presenting with ASBO from 2010 to 2019 utilizing the Pediatric Health Information System. Multivariable mixed-effects logistic regression was performed assessing inter-hospital variability in operative-vs-nonoperative management of ASBO.

RESULTS

Among 6410 pediatric ASBO admissions identified at 46 hospitals, 3,239 (50.5%) underwent surgery during that admission. The hospital-specific rate of surgery ranged from 35.3% (95%CI: 28.5-42.6%) to 74.7% (66.3-81.6%) in the unadjusted model (p < 0.001), and from 35.1% (26.3-45.1%) to 73.9% (66.7-79.9%) in the adjusted model (p < 0.001). Factors associated with operative management for ASBO included admission to a surgical service (OR 2.8 [95%CI: 2.4-3.2], p < 0.001), congenital intestinal and/or rotational anomaly (OR 2.5 [2.1-3.1], p < 0.001), diagnostic workup including advanced abdominal imaging (OR 1.7 [1.5-1.9], p < 0.001), non-emergent admission status (OR 1.5 [1.3-1.8], p < 0.001), and increasing number of complex chronic comorbidities (OR 1.3 [1.2-1.4], p < 0.001). Factors associated with nonoperative management for ASBO included increased hospital-specific annual ASBO volume (OR 0.98 [95%CI: 0.97-0.99], p = 0.002), older age (OR 0.97 [0.96-0.98], p < 0.001), public insurance (OR 0.87 [0.78-0.96], p = 0.008), and presence of coinciding non-intestinal congenital anomalies, neurologic/neuromuscular disease, and/or medical technology dependence (OR 0.57 [95%CI: 0.47-0.68], p < 0.001).

CONCLUSIONS

Rates of surgical intervention for ASBO vary significantly across tertiary children's hospitals in the United States. The variability was independent of patient and hospital characteristics and is likely due to practice variation.

LEVEL OF EVIDENCE

III.

Dose constraints for whole breast radiation therapy based on the quality assessment of treatment plans in the randomised Danish breast cancer group (DBCG) HYPO trial

Purpose

Quality assessment of the treatment plans in the Danish Breast Cancer Group (DBCG) HYPO trial was carried out based on prospectively reported dosimetric parameters and evidence-based dose constraints for whole breast radiation therapy were derived.

Materials and methods

From 2009 to 2014, 1882 patients (pts) were randomised between 50 Gy/25fractions (fr) versus 40 Gy/15fr. Doses to CTVp_breast (V_95%, V_107%-V_110%, D_max, and in addition for 40 Gy plans V_105%-V_107%), ipsilateral lung (V_20Gy/V_17Gy), heart (V_20Gy/V_17Gy, V_40Gy/V_35Gy), and left anterior descending coronary artery (LADCA) (D_max) and use of respiratory gated technique were prospectively reported to the DBCG database. After end of accrual, these dosimetric parameters from all plans in the trial were compared to the pre-specified treatment constraints.

Results

In total, 1854 pts from eight radiation therapy (RT) centres in three countries were treated. No statistically significant differences were found between the results for 40 Gy and 50 Gy plans, except for CTVp_breast hot-spot volume (V_107%-V_110%). Of the 40 Gy pts, 90% with CTVp_breast > 600 mL and 95% with CTVp_breast ≤ 600 mL had a CTVp_breast hot-spot volume (V_105%-V_107%) <2%. In 95% of the 50 Gy plans, the CTVp_breast absolute hot-spot volume (V_107%-V_110%) was <0.5 mL and 1.7 mL for CTVp_breast ≤ 600 mL and > 600 mL, respectively. Compliance was >99% for both heart and lung constraints. Largest deviation from protocol constraints was found for the volume of CTVp_breast covered with 95% of the prescription dose or more (V_95%). The CTV dose coverage (V_95%) was >94.3% in 95% of the right-sided pts, whereas the figures for 95% of the left-sided pts treated with and without respiratory gating were 93.2% and 88.8%, respectively.

Conclusion

A high degree of compliance with protocol dose constraints was found for treatment plans in the DBCG HYPO trial. New constraints for dose to organs at risk and high-dose volumes in the breast are suggested for breast-only RT planning.

Reliability of dose volume constraint inference from clinical data

Dose volume histogram points (DVHPs) frequently serve as dose constraints in radiotherapy treatment planning. An experiment was designed to investigate the reliability of DVHP inference from clinical data for multiple cohort sizes and complication incidence rates. The experimental background was radiation pneumonitis in non-small cell lung cancer and the DVHP inference method was based on logistic regression. From 102 NSCLC real-life dose distributions and a postulated DVHP model, an 'ideal' cohort was generated where the most predictive model was equal to the postulated model. A bootstrap and a Cohort Replication Monte Carlo (CoRepMC) approach were applied to create 1000 equally sized populations each. The cohorts were then analyzed to establish inference frequency distributions. This was applied to nine scenarios for cohort sizes of 102 (1), 500 (2) to 2000 (3) patients (by sampling with replacement) and three postulated DVHP models. The Bootstrap was repeated for a 'non-ideal' cohort, where the most predictive model did not coincide with the postulated model. The Bootstrap produced chaotic results for all models of cohort size 1 for both the ideal and non-ideal cohorts. For cohort size 2 and 3, the distributions for all populations were more concentrated around the postulated DVHP. For the CoRepMC, the inference frequency increased with cohort size and incidence rate. Correct inference rates  >[Formula: see text] were only achieved by cohorts with more than 500 patients. Both Bootstrap and CoRepMC indicate that inference of the correct or approximate DVHP for typical cohort sizes is highly uncertain. CoRepMC results were less spurious than Bootstrap results, demonstrating the large influence that randomness in dose-response has on the statistical analysis.

C9orf72 is required for proper macrophage and microglial function in mice

Expansions of a hexanucleotide repeat (GGGGCC) in the noncoding region of the C9orf72 gene are the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia. Decreased expression of C9orf72 is seen in expansion carriers, suggesting that loss of function may play a role in disease. We found that two independent mouse lines lacking the C9orf72 ortholog (3110043O21Rik) in all tissues developed normally and aged without motor neuron disease. Instead, C9orf72 null mice developed progressive splenomegaly and lymphadenopathy with accumulation of engorged macrophage-like cells. C9orf72 expression was highest in myeloid cells, and the loss of C9orf72 led to lysosomal accumulation and altered immune responses in macrophages and microglia, with age-related neuroinflammation similar to C9orf72 ALS but not sporadic ALS human patient tissue. Thus, C9orf72 is required for the normal function of myeloid cells, and altered microglial function may contribute to neurodegeneration in C9orf72 expansion carriers.

Abstract 4205: The Jackson Laboratory Repository: new mouse models of cancer

The Jackson Laboratory Repository serves as a centralized facility to import, develop, preserve, and distribute mouse models to the scientific community. More than 400 strains are added annually to one of the largest collection of characterized mouse strains available.

New models of increased tumor incidence at the Repository include three transgenic strains for studies of prostate tumorogenesis that use the rat probasin promoter, (Pbsn-ERG*) develops prostate neoplasia resulting from the expression of the ERG oncogene in prostate epithelial cells; a companion strain that expresses hepsin and GFP in prostate epithelial cells (Pbsn-Hpn,-GFP); a transgenic (Pbsn-IGF1*) that develops prostate hyperplasia; a B cell lymphoma transgenic model expressing the human T-cell leukemia/lymphoma 1 gene (Cd79b-TCL1A); a mouse with a targeted mutation in the kinase Plk3 that develops spontaneous tumors in multiple organs (lung, kidney, liver); a mouse with a targeted mutation in Xpc that exhibits increased susceptibility to radiation induced skin cancer and acetylaminofluorene-induced lung and liver cancers; and a targeted mutation in the tumor suppressor, Tnk1, that develops high rates of spontaneous tumors (lymphomas and carcinomas).

Other recently added mutants allow cancer research in different areas ranging from an amino acid substitution (S10A) in Cdkn1b (p27) that reduces susceptibility to induced lung tumors to new research tools, which include a tetracycline (tetO) regulated Erbb2 (TRE-Neu) transgenic strain that develops hyperplasia in tissues where Erbb2 is expressed when combined with a tTA/rtTA strain, and a transgenic mouse, which expresses human ERBB2 (HER2) in mammary gland and brain, displays tolerance to ERBB2 antigen and may be useful in testing ERBB2-based vaccines and immunotherapies.

Equally important are the Cre recombinase-expressing strains used in conjunction with these mutants. Most of the existing Cre strains have not been fully characterized and ‘ectopic’ expression of Cre recombinase can confound analysis of experimental results. The Repository has undertaken a project to comprehensively characterize Cre recombinase activity in embryonic and adult mouse tissues. Annotated images are being published on a dedicated website and submitted to MGI as part of a collaboration to develop a Cre stain database (http://www.creportal.org/). This information will allow users to make informed judgments about the suitability of a particular line for their experiments.

The Repository maintains a searchable on-line resource (www.jaxmice.jax.org/query). Researchers wishing to have strains considered for inclusion in the Repository are encouraged to submit their strains at: www.jax.org/grc/.

The Jackson Laboratory Repository is supported by the NCRR, The Howard Hughes Medical Institute, The Ellison Medical Foundation and donations from private charitable foundations.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4205.

Two novel alleles of tottering with distinct Ca(v)2.1 calcium channel neuropathologies

The calcium channel CACNA1A gene encodes the pore-forming, voltage-sensitive subunit of the voltage-dependent calcium Ca(v)2.1 type channel. Mutations in this gene have been linked to several human disorders, including familial hemiplegic migraine, episodic ataxia 2 and spinocerebellar ataxia type 6. The mouse homologue, Cacna1a, is associated with the tottering, Cacna1a(tg), mutant series. Here we describe two new missense mutant alleles, Cacna1a(tg-4J) and Cacna1a(Tg-5J). The Cacna1a(tg-4J) mutation is a valine to alanine mutation at amino acid 581, in segment S5 of domain II. The recessive Cacna1a(tg-4J) mutant exhibited the ataxia, paroxysmal dyskinesia and absence seizures reminiscent of the original tottering mouse. The Cacna1a(tg-4J) mutant also showed altered activation and inactivation kinetics of the Ca(v)2.1 channel, not previously reported for other tottering alleles. The semi-dominant Cacna1a(Tg-5J) mutation changed a conserved arginine residue to glutamine at amino acid 1252 within segment S4 of domain III. The heterozygous mouse was ataxic and homozygotes rarely survived. The Cacna1a(Tg-5J) mutation caused a shift in both voltage activation and inactivation to lower voltages, showing that this arginine residue is critical for sensing Ca(v)2.1 voltage changes. These two tottering mouse models illustrate how novel allelic variants can contribute to functional studies of the Ca(v)2.1 calcium channel.

The Mouse Genome Database (MGD): integrating biology with the genome

The Mouse Genome Database (MGD) is one component of the Mouse Genome Informatics (MGI) system (http://www.informatics.jax.org), a community database resource for the laboratory mouse. MGD strives to provide a comprehensive knowledgebase about the mouse with experiments and data annotated from both literature and online sources. MGD curates and presents consensus and experimental data representations of genetic, genotype (sequence) and phenotype information including highly detailed reports about genes and gene products. Primary foci of integration are through representations of relationships between genes, sequences and phenotypes. MGD collaborates with other bioinformatics groups to curate a definitive set of information about the laboratory mouse and to build and implement the data and semantic standards that are essential for comparative genome analysis. Recent developments in MGD discussed here include an extensive integration of the mouse sequence data and substantial revisions in the presentation, query and visualization of sequence data.

Decreased (45)Ca(2)(+) uptake in P/Q-type calcium channels in homozygous lethargic (Cacnb4lh) mice is associated with increased beta3 and decreased beta4 calcium channel subunit mRNA expression

The mutated gene in the lethargic (Cacnb4lh) mouse model of absence seizures encodes the beta4 subunit of voltage-gated calcium channels (VGCCs), leading to decreased mRNA expression of a beta4 subunit that is truncated and cannot bind to alpha1 subunits of VGCCs. In this study we accomplished two goals. First, we studied the functional consequence of altered VGCCs by examining the effects of a selective P/Q-type channel antagonist on KCl-induced (45)Ca(2)(+) uptake in brain synaptosomes from Cacnb4lh homozygotes and non-epileptic controls (designated by +/+). We found that depolarization-induced (45)Ca(2)(+) uptake was significantly reduced in the brains of Cacnb4lh homozygotes, and that the reduced uptake was completely accounted for by reduced function of P/Q-type calcium channel. Second, we examined VGCC subunit composition to determine if other subunits were altered in addition to the mutation affecting beta4 subunits in Cacnb4lh homozygotes; when alterations were found, we determined if they were regional or global. We used in situ hybridization histochemistry (ISHH) to analyze the neuro-anatomic distribution of beta4, beta1b, beta2, beta3, alpha1A, alpha1B, alpha1C, alpha1E, and alpha1G subunit mRNAs in brain sections from matched Cacnb4lh homozygotes and +/+ controls. Our results indicated that expression of beta4 subunit mRNA is globally reduced throughout the brains of Cacnb4lh homozygotes, in contrast to a small but significant global increase in the expression of beta3 subunit mRNA. There were no significant differences in expression of the other VGCC subunit mRNAs examined. Together, these findings indicate that a host of changes in VGCC subunit composition accompany reduced function of P/Q-type channels in homozygous lethargic mice.

Altered calcium channel currents in Purkinje cells of the neurological mutant mouse leaner

Mutations of the alpha1A calcium channel subunit have been shown to cause such human neurological diseases as familial hemiplegic migraine, episodic ataxia-2, and spinocerebellar ataxia 6 and also to cause the murine neurological phenotypes of tottering and leaner. The leaner phenotype is recessive and characterized by ataxia with cortical spike and wave discharges (similar to absence epilepsy in humans) and a gradual degeneration of cerebellar Purkinje and granule cells. The mutation responsible is a single-base substitution that produces truncation of the normal open reading frame beyond repeat IV and expression of a novel C-terminal sequence. Here, we have used whole-cell recordings to determine whether the leaner mutation alters calcium channel currents in cerebellar Purkinje cells, both because these cells are profoundly affected in leaner mice and because they normally express high levels of alpha1A. In Purkinje cells from normal mice, 82% of the whole-cell current was blocked by 100 nM omega-agatoxin-IVA. In Purkinje cells from homozygous leaner mice, this omega-agatoxin-IVA-sensitive current was 65% smaller than in control cells. Although attenuated, the omega-agatoxin-IVA-sensitive current in homozygous leaner cells had properties indistinguishable from that of normal Purkinje neurons. Additionally, the omega-agatoxin-IVA-insensitive current was unaffected in homozygous leaner mice. Thus, the leaner mutation selectively reduces P-type currents in Purkinje cells, and the alpha1A subunit and P-type current appear to be essential for normal cerebellar function.

Neuropeptide Y receptor genes mapped in human and mouse: receptors with high affinity for pancreatic polypeptide are not clustered with receptors specific for neuropeptide Y and peptide YY

Ppyr1, Npy5r, and Npy6r, the genes encoding mouse type 4, type 5, and type 6 members of the neuropeptide Y receptor family, have been mapped by interspecific backcross analysis to conserved linkage groups on mouse Chr 14, Chr 8, and Chr 18, respectively. The human genes, PPYR1 and NPY5R, have been localized to chromosomes 10q and 4q, respectively, by analysis of a panel of rodent-human somatic cell hybrids and yeast artificial chromosomes. These studies complete the mapping of the cloned NPY receptor subtypes in human and mouse and, together with previous studies, establish that the genes encoding receptors with high affinity for pancreatic polypeptide are not clustered with the genes encoding receptors specific for neuropeptide Y and peptide YY. The physical association of these receptor genes correlates with ligand-binding properties, rather than sequence identity, and suggests a complex evolutionary relationship.

Sodium/hydrogen exchanger gene defect in slow-wave epilepsy mutant mice

The "housekeeping" sodium/hydrogen exchanger, NHE1, mediates the electroneutral 1:1 exchange of Na+ and H+ across the plasma membrane. NHE1 is ubiquitous and is studied extensively for regulation of pHi, cell volume, and response to growth factors. We describe a spontaneous mouse mutant, slow-wave epilepsy, (swe), with a neurological syndrome including ataxia and a unique epilepsy phenotype consisting of 3/sec absence and tonic-clonic seizures. swe was fine-mapped on Chromosome 4 and identified as a null allele of Nhe1. Mutants show selective neuronal death in the cerebellum and brainstem but otherwise are healthy. This first example of a disease-causing mutation in an Nhe gene provides a new tool for studying the delicate balance of neuroexcitability and cell survival within the CNS.

Neuropeptide Y receptor genes on human chromosome 4q31-q32 map to conserved linkage groups on mouse chromosomes 3 and 8

Npy1r and Npy2r, the genes encoding mouse type 1 and type 2 neuropeptide Y receptors, have been mapped by interspecific backcross analysis. Previous studies have localized the human genes encoding these receptors to chromosome 4q31-q32. We have now assigned Npy1r and Npy2r to conserved linkage groups on mouse Chr 8 and Chr 3, respectively, which correspond to the distal region of human chromosome 4q. Using yeast artificial chromosomes, we have estimated the distance between the human genes to be approximately 6 cM. Although ancient tandem duplication events may account for some closely spaced G-protein-coupled receptor genes, the large genetic distance between the human type 1 and type 2 neuropeptide Y receptor genes raises questions about whether this mechanism accounts for their proximity.

Absence epilepsy in tottering mutant mice is associated with calcium channel defects

Mutations at the mouse tottering (tg) locus cause a delayed-onset, recessive neurological disorder resulting in ataxia, motor seizures, and behavioral absence seizures resembling petit mal epilepsy in humans. A more severe allele, leaner (tg(la)), also shows a slow, selective degeneration of cerebellar neurons. By positional cloning, we have identified an alpha1A voltage-sensitive calcium channel gene that is mutated in tg and tg(la) mice. The alpha1A gene is widely expressed in the central nervous system with prominent, uniform expression in the cerebellum. alpha1A expression does not mirror the localized pattern of cerebellar degeneration observed in tg(la) mice, providing evidence for regional differences in biological function of alpha1A channels. These studies define the first mutations in a mammalian central nervous system-specific voltage-sensitive calcium channel and identify the first gene involved in absence epilepsy.

New seizure frequency QTL and the complex genetics of epilepsy in EL mice

EL/Suz (EL) mice experience recurrent seizures that are similar to common partial complex epilepsy in humans. In the mice, seizures occur naturally at 90-100 days of age, but can be induced in younger mice and analyzed as a semi-quantitative trait after gentle rhythmic stimulation. A previous genetic mapping study of EL backcrosses to the strains ABP/LeJ or DBA/2J showed two quantitative trait loci (QTL) with large effects on seizure frequency (El1, Chr 9; El2, Chr 2) and implied the existence of other QTL with lesser effects. To further the understanding of EL-derived seizure alleles, we examined intercross progeny of EL and the strains ABP/LeJ and DDY/Jcl, and also a backcross of (EL x DDY)F1 hybrids to DDY. A new large-effect seizure frequency QTL was found (El5, Chr 14), a more minor QTL confirmed (El3, Chr 10), and two additional QTL proposed (El4, Chr 9; El6, Chr 11). The serotonin receptor gene, Htr2a, maps near and is a candidate for El5, and linkages of other serotonin receptor genes to seizure frequency QTL are noted. In addition, a strong gender effect was revealed, and epistasis was found between Chr 9 and Chr 14 markers. Despite this progress, however, our results revealed a more complex determinism of epilepsy in EL mice than previously described. In particular, no single El locus or pair was essential for frequent seizures, as QTL with large effects, such as El5, El2, and El1, were highly dependent on genetic context. Our studies highlight the importance of gene interaction in some complex mammalian traits defined by natural variation.

Congenic strains reveal effects of the epilepsy quantitative trait locus, El2, separate from other El loci

Congenic mouse strains made by transferring epilepsy predisposing alleles El1, El2, and El3 from the EL/Suz strain to the ABP/Le recipient were tested for seizure frequency following gentle rhythmic stimulation. Mice homozygous for El2, but not El1 or El3, experienced seizures much more frequently than ABP controls, while respective El1 homozygotes and El2 heterozygotes had only a modest increase over ABP, and El3 homozygotes showed no increase. Association between marker genotypes and seizure frequency in small intra-strain crosses showed that the phenotypic effects of El2 map to the selected interval, and that segregation of El2 accounts for virtually all genetic effects. However, in separating El2 from other EL susceptibility alleles, the seizure frequency phenotype was weaker and less heritable than in crosses between parental strains. These results confirm El2 as an important QTL and show that it has significant phenotypic effects in the absence of other EL-derived alleles, including El1. In addition, the present localization of El2 on Chr 2 suggests several potential candidate genes for El2, including the beta subunit of phospholipase-C. The approach to dissecting complex traits by making congenic strains for individual QTL is discussed.

Genetic epilepsy model derived from common inbred mouse strains

The recombinant inbred mouse strain, SWXL-4, exhibits tonic-clonic and generalized seizures similar to the commonest epilepsies in humans. In SWXL-4 animals, seizures are observed following routine handling at about 80 days of age and may be induced as early as 55 days by rhythmic gentle tossing. Seizures are accompanied by rapid, bilateral high frequency spike cortical discharges and followed by a quiescent post-ictal phase. Immunohistochemistry of the immediate early gene products c-Fos and c-Jun revealed abnormal activation within cortical and limbic structures. The seizure phenotype of SWXL-4 can be explained and replicated fully by the inheritance of susceptibility alleles from its progenitor strains, SWR/J and C57L/J. Outcrosses of SWXL-4 with most other common inbred strains result in F1 hybrids that have seizure at least as frequently as SWXL-4 itself. Quantitative trait locus mapping reveals a seizure frequency determinant, Szf1, near the pink-eyed dilution locus on chromosome 7, accounting for up to 32% of the genetic variance in an F2 intercross between SWXL-4 and the linkage testing strain ABP/Le. These studies demonstrate that common strains of mice such as SWR and C57L contain latent epilepsy susceptibility alleles. Although the inheritance of susceptibility may be complex, these results imply that a number of potentially important and practical, noninvasive models for this disorder can be constructed and studied in crosses between common mouse strains.

Transcription vectors that facilitate the identification and mapping of RNA splice sites in genomic DNA

Two transcription vectors were constructed that can identify the splice sites at exon-intron boundaries of inserted DNA fragments possessing the complementary splice site. One vector contains the 5' splice donor site and flanking exon-intron sequences from the 3' end of the adenovirus first late leader. The other vector contains the 3' splice acceptor site and the branch acceptor site, plus the flanking exon-intron sequences from the 5' end of the adenovirus second late leader. Both vectors contain a multiple cloning site for insertion of DNA fragments. DNA fragments supplying the complementary splice site, including the adjacent exon and intron sequences, were inserted into the vectors. The vectors were used as templates for the synthesis of chimeric RNA transcripts that were spliced in in vitro splicing extracts. Chimeric transcripts from the vectors containing complementary splice site boundary regions from the human growth hormone gene were accurately spliced in vitro. A splice site from a human growth hormone intron that is not normally spliced in vitro was spliced when paired with an adenovirus splice site. These vectors can be used to identify splice sites and to determine the lengths of exons and their attached introns within a DNA fragment of unknown coding content.