Biochemical, phenotypic and neurophysiological characterization of a genetic mouse model of RSH/Smith--Lemli--Opitz syndrome

The RSH/Smith--Lemli--Opitz syndrome (RSH/SLOS) is a human autosomal recessive syndrome characterized by multiple malformations, a distinct behavioral phenotype with autistic features and mental retardation. RSH/SLOS is due to an inborn error of cholesterol biosynthesis caused by mutation of the 3 beta-hydroxysterol Delta(7)-reductase gene. To further our understanding of the developmental and neurological processes that underlie the pathophysiology of this disorder, we have developed a mouse model of RSH/SLOS by disruption of the 3 beta-hydroxysterol Delta(7)-reductase gene. Here we provide the biochemical, phenotypic and neurophysiological characterization of this genetic mouse model. As in human patients, the RSH/SLOS mouse has a marked reduction of serum and tissue cholesterol levels and a marked increase of serum and tissue 7-dehydrocholesterol levels. Phenotypic similarities between this mouse model and the human syndrome include intra-uterine growth retardation, variable craniofacial anomalies including cleft palate, poor feeding with an uncoordinated suck, hypotonia and decreased movement. Neurophysiological studies showed that although the response of frontal cortex neurons to the neurotransmitter gamma-amino-n-butyric acid was normal, the response of these same neurons to glutamate was significantly impaired. This finding provides insight into potential mechanisms underlying the neurological dysfunction seen in this human mental retardation syndrome and suggests that this mouse model will allow the testing of potential therapeutic interventions.

Ophthalmic drops causing coma in an infant

A 1-month-old infant with Peters anomaly had recurrent episodes of unresponsiveness, hypotension, hypotonia, hypothermia, and bradycardia. An extensive medical evaluation determined these episodes to be caused by brimonidine, an anti-glaucoma agent. There is the potential for serious toxic effects from the systemic absorption of topically applied ophthalmic agents in children.

Laboratory evaluation of urea cycle disorders

The urea cycle disorders (UCDs) represent a group of inherited metabolic diseases with hyperammonemia as the primary laboratory abnormality. Affected individuals may become comatose or die if not treated rapidly. Diagnosis of a UCD requires a high index of suspicion and judicious use of the laboratory. It is important to rule out other conditions causing hyperammonemia that may require different treatment. The astute clinician may suspect a specific UCD in the appropriate clinical setting, but only laboratory results can confirm a specific diagnosis. The importance of the laboratory in helping the clinician to differentiate among various causes of hyperammonemia, in confirming a specific UCD, in carrier testing, and in prenatal diagnostic testing is highlighted in this review.

Long-term management of patients with urea cycle disorders

The long-term treatment of patients with urea cycle disorders (UCDs) includes diet treatment and use of specific medications. Guidelines are provided for patients with a severe phenotype. However, treatment must be tailored for each individual, especially with regard to residual enzyme function and in vivo metabolic capacity. This will be reflected in tests used for monitoring therapy that should be performed on a periodic basis. The goal of therapy is to eliminate chronic complications, a laudable but rarely attainable goal. Sick-day rules are discussed. Chronic management also includes diverse services that are essential to the success of the metabolic program. These include neurologic and developmental evaluations, feeding team evaluation and therapy, physical and occupational therapies, speech therapy, school and educational services, social service intervention, psychologic services, and genetic counseling.

Carrier frequency of the common mutation IVS8-1G>C in DHCR7 and estimate of the expected incidence of Smith-Lemli-Opitz syndrome

Smith-Lemli-Opitz syndrome (SLOS) is a multiple congenital anomaly/mental retardation syndrome of variable severity with an incidence previously estimated at 1 in 20,000-60,000 based on case frequency surveys. Identification of the gene defect in SLOS has made it possible to calculate the carrier frequency and estimate disease incidence using molecular methods to identify carriers. Using a previously described PCR-RFLP assay we screened 1503 anonymous blood samples from random newborn screening blood spot cards for the presence of the common SLOS mutation IVS8-1G>C in order to determine the carrier frequency. Sixteen carriers were identified in the 1503 samples. Since the frequency of the IVS8-1G>C mutation among all SLOS gene mutations is known, the overall carrier frequency for all mutations can be calculated. The calculated carrier frequency for all mutations based on this result is 1 in 30, predicting an SLOS incidence of 1 in 1590 to 1 in 13,500. The current incidence estimate may, therefore, significantly underestimate the true incidence of SLOS. This discrepancy between calculated and observed incidence could be due to undiagnosed mild cases, misdiagnosed severe cases, death prior to diagnosis, or fetal loss. More comprehensive incidence studies are needed to determine if SLOS is as common as predicted by the very high (1 in 30) carrier frequency determined in this study.

Risk factors for premature ovarian failure in females with galactosemia

The risk for premature ovarian failure (POF) in females with galactosemia can be predicted by analyzing 3 areas of risk pathology: the patient's molecular genotype for galactose-1-phosphate uridyltransferase (GALT), alternate pathways for galactose metabolism, and the patient's environment at diagnosis and during treatment.

STUDY DESIGN

Retrospective cross-sectional information was collected on 53 females with classic galactosemia, and their ovarian function was analyzed by determination of serum follicle-stimulating hormone and luteinizing hormone levels and by clinical observation. The associations were analyzed between POF and the mutations in GALT, the highest erythrocyte galactose-1-phosphate (Gal-1-P) level at diagnosis, the age at which dietary treatment was initiated, mean erythrocyte Gal-1-P level during treatment, and whole-body carbon 13-labeled galactose oxidation to (13)CO(2).

RESULTS

The most prevalent mutation, Q188R, had a significant effect of genotype category (Q188R/Q188R, Q188R/Other, Other/Other) on POF (P =.04, Fisher exact test and an odds ratio of 8.3). Mean erythrocyte Gal-1-P level during treatment was a significant risk factor for POF (P =.04). Also, all patients studied with less than 5% total body oxidation of galactose to (13)CO(2) had POF, whereas those with more than 5% did not have POF (P =.008, Fisher exact test).

CONCLUSION

The development of POF in females with galactosemia is more likely if the patient's genotype is Q188R/Q188R, if the mean erythrocyte Gal-1-P is >3.5 mg/dL during therapy, and if the recovery of (13)CO(2) from whole-body (13)C-galactose oxidation is reduced below 5% of administered (13)C-galactose.

Mutation analysis and description of sixteen RSH/Smith-Lemli-Opitz syndrome patients: polymerase chain reaction-based assays to simplify genotyping

We report the clinical and molecular data of 16 patients with RSH/Smith-Lemli-Opitz syndrome (RSH/SLOS) with varying phenotypic severity, for which we have identified mutations in both alleles. RSH/SLOS is an autosomal recessive malformation syndrome caused by mutations in the gene encoding the sterol Delta(7)-reductase. This protein catalyzes the reduction of 7-dehydrocholesterol to cholesterol in the last step of cholesterol biosynthesis via the Kandutsch-Russell pathway. In addition to previously reported mutations (T93M, L109P, G147D, W151X, T154M, R242C, A247V, T289I, IVS8-1G-->C, Y408H, and E448K), we have identified six previously undescribed mutations (321G-->C, W177R, R242H, Y318N, L341P, and C444Y). We also report rapid polymerase chain reaction (PCR)-based assays developed to detect four of the recurring mutations (T93M, W151X, V326L, and R404C) and six other RSH/SLOS mutations (321G-->C, L109P, T154M, T289I, Y318N, and L341P). The purpose of this article is to correlate detailed clinical information with molecular data in order to improve our understanding of the genotype-phenotype correlation of RSH/SLOS and to report the development of PCR-based assays that will allow more rapid mutation analysis.

Sterol balance in the Smith-Lemli-Opitz syndrome. Reduction in whole body cholesterol synthesis and normal bile acid production

The Smith-Lemli-Opitz syndrome (SLOS) is a multiple malformation/mental retardation syndrome caused by a deficiency of the enzyme 7-dehydrocholesterol Delta(7)-reductase. This enzyme converts 7-dehydrocholesterol (7-DHC) to cholesterol in the last step in cholesterol biosynthesis. The pathology of this condition may result from two different factors: the deficiency of cholesterol itself and/or the accumulation of precursor sterols such as 7-DHC. Although cholesterol synthesis is defective in cultured SLOS cells, to date there has been no evidence of decreased whole body cholesterol synthesis in SLOS and only incomplete information on the synthesis of 7-DHC and bile acids. In this first report of the sterol balance in SLOS, we measured the synthesis of cholesterol, other sterols, and bile acids in eight SLOS subjects and six normal children. The diets were very low in cholesterol content and precisely controlled. Cholesterol synthesis in SLOS subjects was significantly reduced when compared with control subjects (8.6 vs. 19.6 mg/kg per day, respectively, P < 0.002). Cholesterol precursors 7-DHC, 8-DHC, and 19-nor-cholestatrienol were synthesized in SLOS subjects (7-DHC synthesis was 1.66 +/- 1.15 mg/kg per day), but not in control subjects. Total sterol synthesis was also reduced in SLOS subjects (12 vs. 20 mg/kg per day, P < 0.022). Bile acid synthesis in SLOS subjects (3.5 mg/kg per day) did not differ significantly from control subjects (4.6 mg/kg per day) and was within the range reported previously in normals. Normal primary and secondary bile acids were identified. This study provides direct evidence that whole body cholesterol synthesis is reduced in patients with SLOS and that the synthesis of 7-DHC and other cholesterol precursors is profoundly increased. It is also the first reported measure of daily bile acid synthesis in SLOS and provides evidence that bile acid supplementation is not likely to be necessary for treatment. These sterol balance studies provide basic information about the biochemical defect in SLOS and strengthen the rationale for the use of dietary cholesterol in its treatment.

Smith-Lemli-Opitz syndrome: the first malformation syndrome associated with defective cholesterol synthesis

Smith-Lemli-Opitz syndrome (SLOS), an autosomal recessive condition with multiple malformations, mental retardation, and growth failure, results from markedly reduced activity of the final enzyme in the cholesterol biosynthetic pathway, 7-dehydrocholesterol reductase (DHCR7). Clinical signs vary in severity, ranging from fetal loss to holoprosencephaly with multiple malformations to isolated syndactyly. The biochemical defect in SLOS is a deficiency of DHCR7, which results in an abnormally low cholesterol level, and increased amounts of intermediates of sterol biosynthesis. Animal models currently exist through the use of cholesterol biosynthesis inhibitors, from which a great deal has been learned. Pregnant rats treated with inhibitors of DHCR7 yield pups that have abnormal sterol profiles and craniofacial abnormalities characteristic of severe SLOS. Biochemical testing of human patients can be performed using gas chromatography/mass spectroscopy (GC/MS) to analyze the sterol content of tissues, amniotic fluid, or cell culture lysate. Numerous mutations have been identified in DHCR7 but seven individual mutations account for 67% of the total mutations reported in the literature. Clinical trials with SLOS are underway, with the goal of increasing the cholesterol concentration in the plasma and tissues through the administration of dietary cholesterol. Thus far, this approach has shown limited efficacy. Nevertheless, the recent identification of the biochemical and molecular genetic basis for SLOS is reason for optimism that the condition may one day yield to treatment.

Cholesterol supplementation with egg yolk increases plasma cholesterol and decreases plasma 7-dehydrocholesterol in Smith-Lemli-Opitz syndrome

Smith-Lemli-Opitz syndrome (SLOS), an autosomal recessive condition comprising multiple malformations, mental retardation, and growth failure, results from reduced activity of the final enzyme in cholesterol biosynthesis, 7-dehydrocholesterol Delta(7)-reductase (DHCR7). Reduced plasma and tissue cholesterol concentrations and accumulation of cholesterol precursors including 7-dehydrocholesterol (7-DHC) are characteristic biochemical abnormalities. While it is still unclear what role these potentially toxic precursors have in the pathogenesis of this disorder, the accumulation of 7-DHC in the brain has been associated with impaired learning in rats and oxidized 7-DHC has been shown to induce growth retardation in cultured rat embryos. We hypothesized that supplemental dietary cholesterol would increase plasma cholesterol levels and suppress synthesis of 7-DHC and other abnormal sterols in individuals with SLOS. After baseline sterol levels were obtained, patients were provided supplemental cholesterol as egg yolk. Plasma sterols were analyzed by capillary-column gas chromatography over time in four children with SLOS. When evaluated at 4-8 weeks after the initiation of cholesterol supplementation, there was a marked increase in mean plasma cholesterol, from 53 mg/dl to 82 mg/dl. While the percent of total sterols as 7-DHC decreased from 15% to 10%, there was no change in total plasma 7-DHC levels. However, when evaluated 35-90 weeks after the institution of cholesterol supplementation, mean plasma 7-DHC decreased, from 11.3 mg/dl to 3.5 mg/dl (-67%, P < 0.05), along with an increase in mean plasma cholesterol from 53 mg/dl to 114 mg/dl (+116%, P < 0.05). These results support the hypothesis that over time dietary cholesterol supplementation from egg yolk increases the plasma cholesterol levels and decreases levels of 7-DHC which may be toxic. These data have important therapeutic implications in the management of SLOS.

2-Methylbutyryl-coenzyme A dehydrogenase deficiency: a new inborn error of L-isoleucine metabolism

An 4-mo-old male was found to have an isolated increase in 2-methylbutyrylglycine (2-MBG) and 2-methylbutyrylcamitine (2-MBC) in physiologic fluids. In vitro oxidation studies in cultured fibroblasts using 13C- and 14C-labeled branched chain amino acids indicated an isolated block in 2-methylbutyryl-CoA dehydrogenase (2-MBCDase). Western blotting revealed absence of 2-MBCDase protein in fibroblast extracts; DNA sequencing identified a single 778 C>T substitution in the 2-MBCDase coding region (778 C>T), substituting phenylalanine for leucine at amino acid 222 (L222F) and absence of enzyme activity for the 2-MBCDase protein expressed in Escherichia coli. Prenatal diagnosis in a subsequent pregnancy suggested an affected female fetus, supporting an autosomal recessive mode of inheritance. These data confirm the first documented case of isolated 2-MBCDase deficiency in humans.

Fructose-1,6-diphosphatase deficiency and glyceroluria: one possible etiology for GIS

Fructose-1,6-diphosphatase (FDPase) deficiency is characterized by episodes of lactic acidemia, hypoglycemia, and ketonuria. Liver biopsy and subsequent enzyme analysis most reliably make the diagnosis. Review of the literature reveals 85 cases. Glycerol intolerance syndrome (GIS) is less well defined. There are only a handful of cases reported. We describe a patient with FDPase deficiency and significant glyceroluria and propose that GIS may be caused by partial deficiency of FDPase.

Fetal demise with Smith-Lemli-Opitz syndrome confirmed by tissue sterol analysis and the absence of measurable 7-dehydrocholesterol Delta(7)-reductase activity in chorionic villi

Smith-Lemli-Opitz syndrome (SLOS), an autosomal recessive condition with multiple malformations, mental retardation, and growth failure, results from markedly reduced activity of the final enzyme in the cholesterol biosynthetic pathway, 7-dehydrocholesterol Delta(7)-reductase (DHCR7). We diagnosed SLOS in a fetus following intrauterine demise at 32 weeks' gestation. Chorionic villus (CV) sampling had been performed at 30 weeks because oligohydramnios and atrioventricular septal defect were noted on fetal ultrasound. On fetal post-mortem examination, a midline U-shaped soft palate cleft, micrognathia, postaxial polydactyly of the fingers with single transverse palmar creases bilaterally, and cutaneous syndactyly of toes two-three bilaterally suggested SLOS. We hypothesized that SLOS could be confirmed by analysis of tissue sterols despite extensive autolysis, and by measurement of enzyme activity in CV cells. Measurement of DHCR7 activity in CV cells was undertaken using ergosterol as a substrate. CV cells were unable to convert any ergosterol to brassicasterol after a 72 h incubation period while control CV cells reduced 12.6-71.8% of ergosterol to brassciasterol in a 72 h period. SLOS was confirmed by measurement of elevated 7-dehydrocholesterol (7-DHC) in the CV cells. Measurements of sterols were made in multiple fetal tissues. All tissues analysed showed elevated 7-DHC with markedly increased 7-DHC/cholesterol ratios.

A simple PCR-based assay allows detection of a common mutation, IVS8-1G-->C, in DHCR7 in Smith-Lemli-Opitz syndrome

Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive multiple malformation disorder. A deficiency of the enzyme 7-dehydrocholesterol delta 7-reductase (DHCR7) is the primary abnormality in SLOS. The gene encoding DHCR7 has been cloned, and we have identified a mutation affecting the splice acceptor site 5' of exon 9 that occurs frequently in affected individuals. We developed a novel PCR-based assay to detect this common mutation in DHCR7. Using this assay, heterozygosity was detected for this mutation in 18 of 26 and homozygosity in 1 of 26 unrelated affected individuals. The high frequency of this mutation is suggestive of either a founder effect in our group of patients or a mutational hotspot. The simplicity and reliability of this assay will allow it to be used as a clinical test to aid in diagnosis of atypical cases, in carrier testing, in prediction of prognosis based on genotype, and in prenatal molecular genetic diagnostic testing.

Eye findings in 8 children and a spontaneously aborted fetus with RSH/Smith-Lemli-Opitz syndrome

We evaluate the ophthalmologic findings in 8 children with RSH/Smith-Lemli-Opitz syndrome (SLOS) and document abnormal concentrations of cholesterol and cholesterol precursors in the ocular tissues in a case of SLOS. The most common ophthalmologic finding was blepharoptosis, which was found in 6 of 8 patients, with the severity ranging from mild to moderate. None of the patients in the present study demonstrated cataracts; none had amblyopia from blepharoptosis. One patient had a right hypertropia with overaction of the inferior oblique muscle. This patient also had optic atrophy and a second patient had bilateral optic nerve hypoplasia. The importance of these findings to the visual function remains to be defined. Sterol analysis from ocular tissues of an aborted fetus with SLOS showed increased 7- and 8-dehydrocholesterol and a low cholesterol concentration in the retinal pigment epithelium, lens, cornea, and sclera. Routine ophthalmologic examination is indicated in SLOS because of the high incidence of abnormalities, most likely due to the abnormal synthesis of cholesterol and cholesterol precursors in the ocular tissues of these patients, as evidenced by sterol analysis of the ocular tissues in a case of SLOS.

Mutations in the human sterol delta7-reductase gene at 11q12-13 cause Smith-Lemli-Opitz syndrome

The Smith-Lemli-Opitz syndrome (SLOS; also known as "RSH syndrome" [MIM 270400]) is an autosomal recessive multiple malformation syndrome due to a defect in cholesterol biosynthesis. Children with SLOS have elevated serum 7-dehydrocholesterol (7-DHC) levels and typically have low serum cholesterol levels. On the basis of this biochemical abnormality, it has been proposed that mutations in the human sterol Delta7-reductase (7-DHC reductase; E.C.1.3.1.21) gene cause SLOS. However, one could also propose a defect in a gene that encodes a protein necessary for either the expression or normal function of sterol Delta7-reductase. We cloned cDNA encoding a human sterol Delta7-reductase (DHCR7) on the basis of its homology with the sterol Delta7-reductase from Arabidopsis thaliana, and we confirmed the enzymatic function of the human gene product by expression in SLOS fibroblasts. SLOS fibroblasts transfected with human sterol Delta7-reductase cDNA showed a significant reduction in 7-DHC levels, compared with those in SLOS fibroblasts transfected with the vector alone. Using radiation-hybrid mapping, we show that the DHCR7 gene is encoded at chromosome 11q12-13. To establish that defects in this gene cause SLOS, we sequenced cDNA clones from SLOS patients. In three unrelated patients we have identified four different mutant alleles. Our results demonstrate both that the cDNA that we have identified encodes the human sterol Delta7-reductase and that mutations in DHCR7 are responsible for at least some cases of SLOS.

Bilateral radial ray hypoplasia with multiple epiphyseal dysplasia

We describe a 5-4/12-year-old girl with the unique combination of bilateral radial ray hypoplasia and multiple epiphyseal dysplasia (MED). Radial ray hypoplasia was diagnosed at birth. MED was documented at age 4-3/12 years when she presented with leg pain and short stature and was found to have femoral anteversion and tibial torsion giving rise to severe genu valgum deformity and intoeing. She has no facial anomalies and is developmentally normal. Family history is unremarkable and chromosomal analysis was normal. Investigation of mineral metabolism showed idiopathic hypercalciuria. Surgical lengthening of her severely hypoplastic left radius at age 19 months was successful. Bilateral femoral and tibial osteotomies at age 5-4/12 years corrected her lower limb deformities. This combination of two distinctive but rare skeletal abnormalities may represent a new syndrome.

Black children deficient in galactose 1-phosphate uridyltransferase: correlation of activity and immunoreactive protein in erythrocytes and leukocytes

A recent study found a high prevalence of a missense mutation (S135L) in the gene for galactose 1-phosphate uridyltransferase (GALT) in black children with galactosemia (J Pediatr 1996; 128:89-95). In the present study, GALT activity and GALT protein content were measured in erythrocytes and leukocytes of eight black and seven white galactosemic (GALT-deficient) children, for correlation with the presence of the S135L and Q188R (highly prevalent in white galactosemic children) missense mutations. The S135L mutation was found in 9 of 16 alleles of black children but not in white children; the Q188R mutation was found in 10 of 14 alleles examined in white galactosemic children and in 4 of 16 alleles in black galactosemic children. The GALT activity was near zero in the erythrocytes of white and black galactosemic children (0.26 +/- 0.28 vs 0.33 +/- 0.25 mumol/hr per gram of hemoglobin, respectively; p = 0.61) (normal 17 to 26 mumol/hr per gram), and no correlation of erythrocyte activity with genotype was observed. The GALT activity was higher in the leukocytes of black galactosemic children compared with white children (5 +/- 6 vs 1 +/- 2 mumol/hr per gram, respectively) (normal 172 to 374 mumol/hr per gram), but the difference was not statistically significant (p = 0.11). Analysis by genotype revealed that the two S135L homozygotes had much more leukocyte activity (9 and 17 mumol/hr per gram) than Q188R homozygotes or than all non-S135L allelic genotypes. Compound heterozygotes (S135L/G) had intermediate activity. The GALT protein was not detectable by Western blot in the erythrocytes of either white or black galactosemic children, as determined by antibodies specific for both C- and N-terminal sequences. The GALT protein was undetectable in the leukocytes of white galactosemic children, but leukocytes from black galactosemic children with the S135L mutation contained reduced but readily detectable GALT protein. Erythrocyte galactose 1-phosphate levels were significantly lower in galactosemic children with an S135L mutant allele (1.1 +/- 0.2 gm/dl) compared with children who had other mutations (3.1 +/- 0.9 mg/dl; p = 0.0001). The correlation of protein content data with activity levels in the blood cells suggests that the S135L missense mutation affects the stability of GALT protein to produce a deficiency state.

Studies of collagen synthesis and structure in the differentiation of child abuse from osteogenesis imperfecta

OBJECTIVE

To determine whether analysis of collagen synthesized by dermal fibroblasts could identify children with osteogenesis imperfecta (OI) among those suspected to have been abused.

METHODS

We reviewed biochemical studies and clinical findings for all children who were referred to us to distinguish OI from abuse during a 4-year period.

RESULTS

Cells from 6 of 48 children tested to distinguish OI from abuse had biochemical evidence of OI. In five of the six children with abnormal results on collagen studies, clinical signs of OI in addition to fractures were present on examination by a physician familiar with the condition. In those five cases, the diagnosis of OI was strongly suspected.

CONCLUSIONS

OI can be diagnosed by biochemical studies in some cases of suspected abuse, but clinical evaluation by experienced physicians is usually sufficient to do so. When diagnostic uncertainty persists in cases of suspected child abuse, biochemical studies may be a useful adjunct, but routine biopsy for children suspected to have been abused is unwarranted.

Nonketotic hyperglycinemia: atypical clinical and biochemical manifestations

A 16-year-old boy had intermittent chorea, delirium, and vertical gaze palsy precipitated by febrile illness. Nonketotic hyperglycinemia was confirmed by measurement of liver and lymphoblast glycine cleavage enzyme activity. Deficient but residual enzyme activity was demonstrated in both tissues, possibly accounting for the mild phenotype. Confirmation of an atypical variant of nonketotic hyperglycinemia with residual glycine cleavage enzyme activity has important implications for diagnosis and treatment.

Klippel-Trenaunay-Weber syndrome associated with a 5:11 balanced translocation

We report on a case of Klippel-Trenaunay Weber syndrome (KTWS) associated with a reciprocal translocation [46,XX,t (5;11) (q13.3;p15.1)]. The patient has developmental delay and minor anomalies in addition to classic findings of KTWS. These data support the notion that Klippel-Trenaunay-Weber syndrome may be due to a single gene defect and suggests the possible localization of a Klippel-Trenaunay-Weber gene(s) to 5q or 11p.