A homozygous variant in the Lamin B receptor gene LBR results in a non-lethal skeletal dysplasia without Pelger-Huët anomaly

Lamin B receptor, a member of the sterol reductase family, is an inner nuclear membrane protein which binds lamin B proteins and is involved in the organization of heterochromatin. Mutations in LBR have been associated with a variety of disorders, such as Pelger-Huët anomaly, a benign abnormality affecting neutrophils, and Greenberg Dysplasia, a lethal condition in the perinatal period. We identified a homozygous LBR missense mutation (NM_002296.4: c.1366C > G, p.(Leu456Val)) in two adult sisters with a Lamin B receptor-related disorder associated with a skeletal dysplasia milder than Greenberg Dysplasia. Individual 1 has short stature with short limbs (mostly rhizomelic for the upper extremities, and mesomelic for the lower extremities), limited elbow extension. She required Achilles tenotomy, and does not have facial dysmorphisms. Individual 2 has similar skeletal features, but also has bowed femurs, osteopenia, spastic paraplegia of the lower limbs, equinovarus feet, a single kidney, neurogenic bladder, obstructive hydronephrosis, scoliosis and syndactyly of the toes. This report provides additional evidence of variability for Lamin B receptor-related disorders associated with a non-lethal skeletal dysplasia without Pelger-Huët anomaly. We describe a novel pathogenic variant that has not been previously associated with disease and demonstrate the effect of this variant on sterol C14-reductase activity.

Novel NSDHL gene variant for congenital hemidysplasia with ichthyosiform erythroderma and limb defects (CHILD) syndrome

We report a case of a 1-year and 2-month-old girl with clinical features consistent with congenital hemidysplasia with ichthyosis and limb defects syndrome. Sterol analysis from skin flakes revealed increased levels of a mono 4-alpha methyl sterol also seen in plasma as well as the presence of 4-alpha-carboxy-4-methyl-cholest-8(9)-en-3beta-ol and several keto-sterols, which are usually below the limit of detection. This sterol pattern is consistent with abnormal function of the 4-alpha-methylsterol-4-demethylase complex. NSDHL gene testing revealed the presence of a variant of uncertain significance, c.130G>A (p.Gly44Ser). This missense mutation currently is not included in population databases (ExAC no frequency) and has not been reported in individuals with an NSDHL-related condition. Parental studies showed that neither parent carries the NSDHL variant. On this basis, this variant has been reclassified as likely pathogenic. Symptomatic treatment with keratolytic agents, emollients and ketoconazole was initiated.

Abnormal lipid processing but normal long-term repopulation potential of myc-/- hepatocytes

Establishing c-Myc's (Myc) role in liver regeneration has proven difficult particularly since the traditional model of partial hepatectomy may provoke an insufficiently demanding proliferative stress. We used a model of hereditary tyrosinemia whereby the affected parenchyma can be gradually replaced by transplanted hepatocytes, which replicate 50-100-fold, over several months. Prior to transplantation, livers from myc−/− (KO) mice were smaller in young animals and larger in older animals relative to myc+/+ (WT) counterparts. KO mice also consumed more oxygen, produced more CO₂ and generated more heat. Although WT and KO hepatocytes showed few mitochondrial structural differences, the latter demonstrated defective electron transport chain function. RNAseq revealed differences in transcripts encoding ribosomal subunits, cytochrome p450 members and enzymes for triglyceride and sterol biosynthesis. KO hepatocytes also accumulated neutral lipids. WT and KO hepatocytes repopulated recipient tyrosinemic livers equally well although the latter were associated with a pro-inflammatory hepatic environment that correlated with worsening lipid accumulation, its extracellular deposition and parenchymal oxidative damage. Our results show Myc to be dispensable for sustained in vivo hepatocyte proliferation but necessary for maintaining normal lipid homeostasis. myc−/− livers resemble those encountered in non-alcoholic fatty liver disease and, under sustained proliferative stress, gradually acquire the features of non-alcoholic steatohepatitis.

Altered cholesterol biosynthesis causes precocious neurogenesis in the developing mouse forebrain

We previously reported a mutation in the cholesterol biosynthesis gene, hydroxysteroid (17-beta) dehydrogenase 7 (Hsd17b7(rudolph)), that results in striking embryonic forebrain dysgenesis. Here we describe abnormal patterns of neuroprogenitor proliferation in the mutant forebrain, namely, a decrease in mitotic cells within the ventricular zone (VZ) and an increase through the remainder of the cortex by E11.5. Further evidence suggests mutant cells undergo abnormal interkinetic nuclear migration (IKNM). Furthermore, intermediate progenitors are increased at the expense of apical progenitors by E12.5, and post-mitotic neurons are expanded by E14.5. In vitro primary neuron culture further supports our model of accelerated cortical differentiation in the mutant. Combined administration of a statin and dietary cholesterol in utero achieved partial reversal of multiple developmental abnormalities in the Hsd17b7(rudolph) embryo, including the forebrain. These results suggest that abnormally increased levels of specific cholesterol precursors in the Hsd17b7(rudolph) embryo cause cortical dysgenesis by altering patterns of neurogenesis.

Abstract B25: Novel hepatic phenotypes caused by conditional c-Myc deletion

The transcription factor c-Myc (hereafter Myc) is among the most frequently deregulated oncoproteins. Inhibition of Myc triggers proliferative arrest of transformed cells and promotes tumor regression and/or apoptosis. Myc is also developmentally necessary and myc-/- embryos die at E9.5-10.5. However, Myc's role in the maintenance of specific tissues has been shown to be of variable importance and necessity. For example, several studies of Myc's role in promoting liver regeneration following partial hepatectomy (PH) have given conflicting results, although all show Myc to be generally dispensable for this function. We have used a conditional murine knockout (KO) model of Myc to study its role in liver regeneration. By employing a mycfl/fl;Alb-Cre+ model in which loss of Myc occurs perinatally, we studied non-oncogenic liver proliferation and metabolism in the absence of Myc signaling.

We employed basic metabolic benchmarks of liver function including measurements of triglyceride levels, oxidative phosphorylation, and TCA cycle and electron transport chain function. At the molecular level, RNAseq was performed on isolated hepatocytes and the mitochondrial proteome was evaluated by both differential and unbiased mass spectrometry. At the time of active Myc excision, myc-/- mice had a significantly lower liver: body weight ratios relative to myc+/+ controls. However, this was reversed in older mice and was associated with the hepatic accumulation of neutral lipids, cholesterol and increased fatty acid β-oxidation in myc-/- mice. RNAseq on hepatocytes and Ingenuity Pathway analyses showed differences in 105 transcripts (q<0.05), the major pathways encoding ribosomal proteins, members of the cytochrome p450 family and enzymes involved in cholesterol and bile metabolism. These findings correlated with abnormalities in fatty acid and sterol metabolism and storage in liver samples.

PH may provide an insufficiently sustained proliferative challenge to allow adequate evaluation of Myc's potential role in liver regeneration. We therefore utilized a mouse model of hereditary tyrosinemia in which knockout of the gene encoding fumarylacetoacetate hydrolase (FAH) leads to hepatocellular death that can be rescued by the infusion of fah+/+ hepatocytes, which expand and eventually replace the fah-/- recipient hepatocytes. FAH-deficient animals could be rescued equally well by both myc+/+ and myc-/- hepatocytes. However, livers from the latter group showed excessive neutral lipid accumulation and fibrosis, reminiscent of non-alcoholic steatohepatitis (NASH). Taken together, our results provide unequivocal evidence that Myc is dispensable for long-term hepatic regeneration but is necessary to maintain proper lipid and steroid metabolism. In Myc's absence the excessive accumulation of these intermediates predisposes to the development of a relatively mild pathology mimicking non-alcoholic fatty liver disease, which under the duress of chronic proliferation, progresses to a more severe NASH-like picture of end-stage liver disease. Our studies thus reveal a heretofore unappreciated role for Myc in hepatic metabolic homeostasis.

Citation Format: Lia R. Edmunds, Lokendra Sharma, Peter Anthony Otero, Sonia D'Souza, James M. Dolezal, Xuemei Zeng, Ying Ding, Fei Ding, Megan E. Beck, Lisa E. Kratz, Jerry Vockley, Eric Goetzman, Donald Scott, Nathan Yates, Andrew W. Duncan, Edward V. Prochownik. Novel hepatic phenotypes caused by conditional c-Myc deletion. [abstract]. In: Proceedings of the AACR Special Conference: Metabolism and Cancer; Jun 7-10, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(1_Suppl):Abstract nr B25.

Endogenous Sterol Metabolites Regulate Growth of EGFR/KRAS-Dependent Tumors via LXR

Meiosis-activating sterols (MAS) are substrates of SC4MOL and NSDHL in the cholesterol pathway and are important for normal organismal development. Oncogenic transformation by epidermal growth factor receptor (EGFR) or RAS increases the demand for cholesterol, suggesting a possibility for metabolic interference. To test this idea in vivo, we ablated Nsdhl in adult keratinocytes expressing KRAS(G12D). Strikingly, Nsdhl inactivation antagonized the growth of skin tumors while having little effect on normal skin. Loss of Nsdhl induced the expression of ATP-binding cassette (ABC) transporters ABCA1 and ABCG1, reduced the expression of low-density lipoprotein receptor (LDLR), decreased intracellular cholesterol, and was dependent on the liver X receptor (LXR) α. Importantly, EGFR signaling opposed LXRα effects on cholesterol homeostasis, whereas an EGFR inhibitor synergized with LXRα agonists in killing cancer cells. Inhibition of SC4MOL or NSDHL, or activation of LXRα by sterol metabolites, can be an effective strategy against carcinomas with activated EGFR-KRAS signaling.

Desmosterolosis: an illustration of diagnostic ambiguity of cholesterol synthesis disorders

Desmosterolosis is an autosomal recessive disorder of cholesterol biosynthesis caused by biallelic mutations of DHCR24 (homozygous or compound heterozygous), which encodes 3-β-hydroxysterol Δ-24-reductase. We report two sisters homozygous for the 571G>A (E191K) DHCR24 mutation. Comparison of the propositae to other reported individuals shows that psychomotor developmental delay, failure to thrive, dysgenesis of the corpus callosum, cerebral white matter atrophy and spasticity likely constitute the minimal desmosterolosis phenotype. The nonspecific features of desmosterolosis make it difficult to suspect clinically and therefore screening for it should be entertained early in the diagnostic evaluation.

Targeting C4-demethylating genes in the cholesterol pathway sensitizes cancer cells to EGF receptor inhibitors via increased EGF receptor degradation

Persistent signaling by the oncogenic EGF receptor (EGFR) is a major source of cancer resistance to EGFR targeting. We established that inactivation of 2 sterol biosynthesis pathway genes, SC4MOL (sterol C4-methyl oxidase-like) and its partner, NSDHL (NADP-dependent steroid dehydrogenase-like), sensitized tumor cells to EGFR inhibitors. Bioinformatics modeling of interactions for the sterol pathway genes in eukaryotes allowed us to hypothesize and then extensively validate an unexpected role for SC4MOL and NSDHL in controlling the signaling, vesicular trafficking, and degradation of EGFR and its dimerization partners, ERBB2 and ERBB3. Metabolic block upstream of SC4MOL with ketoconazole or CYP51A1 siRNA rescued cancer cell viability and EGFR degradation. Inactivation of SC4MOL markedly sensitized A431 xenografts to cetuximab, a therapeutic anti-EGFR antibody. Analysis of Nsdhl-deficient Bpa(1H/+) mice confirmed dramatic and selective loss of internalized platelet-derived growth factor receptor in fibroblasts, and reduced activation of EGFR and its effectors in regions of skin lacking NSDHL.

SIGNIFICANCE

This work identifies a critical role for SC4MOL and NSDHL in the regulation of EGFR signaling and endocytic trafficking and suggests novel strategies to increase the potency of EGFR antagonists in tumors.

Targeting C4-demethylating genes in the cholesterol pathway sensitizes cancer cells to EGF receptor inhibitors via increased EGF receptor degradation

Persistent signaling by the oncogenic EGF receptor (EGFR) is a major source of cancer resistance to EGFR targeting. We established that inactivation of 2 sterol biosynthesis pathway genes, SC4MOL (sterol C4-methyl oxidase-like) and its partner, NSDHL (NADP-dependent steroid dehydrogenase-like), sensitized tumor cells to EGFR inhibitors. Bioinformatics modeling of interactions for the sterol pathway genes in eukaryotes allowed us to hypothesize and then extensively validate an unexpected role for SC4MOL and NSDHL in controlling the signaling, vesicular trafficking, and degradation of EGFR and its dimerization partners, ERBB2 and ERBB3. Metabolic block upstream of SC4MOL with ketoconazole or CYP51A1 siRNA rescued cancer cell viability and EGFR degradation. Inactivation of SC4MOL markedly sensitized A431 xenografts to cetuximab, a therapeutic anti-EGFR antibody. Analysis of Nsdhl-deficient Bpa(1H/+) mice confirmed dramatic and selective loss of internalized platelet-derived growth factor receptor in fibroblasts, and reduced activation of EGFR and its effectors in regions of skin lacking NSDHL.

SIGNIFICANCE

This work identifies a critical role for SC4MOL and NSDHL in the regulation of EGFR signaling and endocytic trafficking and suggests novel strategies to increase the potency of EGFR antagonists in tumors.

Hepatitis C virus selectively perturbs the distal cholesterol synthesis pathway in a genotype-specific manner

Hepatitis C virus (HCV) subverts host cholesterol metabolism for key processes in its lifecycle. How this interference results in the frequently observed, genotype-dependent clinical sequelae of hypocholesterolemia, hepatic steatosis, and insulin resistance (IR) remains incompletely understood. Hypocholesterolemia typically resolves after sustained viral response (SVR), implicating viral interference in host lipid metabolism. Using a targeted cholesterol metabolomic platform we evaluated paired HCV genotype 2 (G2) and G3 patient sera for changes in in vivo HCV sterol pathway metabolites. We compared HCV genotypic differences in baseline metabolites and following antiviral treatment to assess whether sterol perturbation resolved after HCV eradication. We linked these metabolites to IR and urine oxidative stress markers. In paired sera from HCV G2 (n = 13) and G3 (n = 20) patients, baseline sterol levels were lower in G3 than G2 for distal metabolites (7-dehyrocholesterol (7DHC) 0.017 versus 0.023 mg/dL; P(adj) = 0.0524, cholesterol 140.9 versus 178.7 mg/dL; P(adj) = 0.0242) but not the proximal metabolite lanosterol. In HCV G3, SVR resulted in increased levels of distal metabolites (cholesterol [Δ55.2 mg/dL; P(adj) = 0.0015], 7DHC [Δ0.0075 mg/dL; P(adj) = 0.0026], lathosterol [Δ0.0430 mg/dL P(adj) = 0.0405]). In contrast, lanosterol was unchanged after SVR (P = 0.9515).

CONCLUSION

HCV G3, but not G2, selectively interferes with the late cholesterol synthesis pathway, evidenced by lower distal sterol metabolites and preserved lanosterol levels. This distal interference resolves with SVR. Normal lanosterol levels provide a signal for the continued proteolysis of 3-hydroxyl-3-methylglutaryl coenzyme A reductase, which may undermine other host responses to increase cholesterol synthesis. These data may provide a hypothesis to explain why hypocholesterolemia persists in chronic HCV infection, particularly in HCV G3, and is not overcome by host cholesterol compensatory mechanisms.

Combined extraction of acyl carnitines and 26:0 lysophosphatidylcholine from dried blood spots: prospective newborn screening for X-linked adrenoleukodystrophy

X-linked adrenoleukodystrophy (X-ALD) is a severe genetic disorder that affects the nervous system, and the adrenal cortex. Newborn screening for X-ALD has been proposed to allow improved diagnosis along with prospective monitoring and treatment for this severe disorder. Newborn dried whole blood spot (DBS) 26:0 lysophosphatidyl choline was validated as a diagnostic marker for X-ALD and other peroxisomal disorders of peroxisomal β-oxidation. In this study, we developed a new one step extraction procedure that simultaneously extracts acyl carnitines and the lysophosphatidyl cholines from DBS. Further analysis of these metabolites has been performed by two different high throughput LC-MS/MS methods. The 26:0 lysophosphatidyl choline levels in this study were consistent with previously published values and discriminate between healthy and abnormal profiles. There is a very minor modification to the original acyl carnitine extraction procedure and our data indicates that there is no significant effect on acyl carnitine levels in DBS. Our new method potentially can be complementary to the current newborn screening panel. It successfully combines the existing method for acyl carnitine analysis and 26:0 lysophosphatidyl choline that can be applied for prospective X-ALD newborn screening.

Cholesterol metabolism is required for intracellular hedgehog signal transduction in vivo

We describe the rudolph mouse, a mutant with striking defects in both central nervous system and skeletal development. Rudolph is an allele of the cholesterol biosynthetic enzyme, hydroxysteroid (17-beta) dehydrogenase 7, which is an intriguing finding given the recent implication of oxysterols in mediating intracellular Hedgehog (Hh) signaling. We see an abnormal sterol profile and decreased Hh target gene induction in the rudolph mutant, both in vivo and in vitro. Reduced Hh signaling has been proposed to contribute to the phenotypes of congenital diseases of cholesterol metabolism. Recent in vitro and pharmacological data also indicate a requirement for intracellular cholesterol synthesis for proper regulation of Hh activity via Smoothened. The data presented here are the first in vivo genetic evidence supporting both of these hypotheses, revealing a role for embryonic cholesterol metabolism in both CNS development and normal Hh signaling.

The molecules and signaling pathways that regulate growth and patterning of the developing embryo are still being elucidated, and one valuable experimental approach is the use of animal models, such as the mouse. We have identified a recessive mutation in the mouse, rudolph, that causes abnormal forebrain development and have determined that the mutated gene encodes hydroxysteroid (17-beta) dehydrogenase 7 gene, an enzyme necessary for cholesterol biosynthesis. Cholesterol is essential for proper signal transduction of the hedgehog family of proteins, key regulators of both developmental biology and tumor progression. We show that hedgehog signaling is diminished in our rudolph mutant. Our conclusions from studying this mouse mutant support two recent hypotheses in developmental biology. First, several human malformation syndromes are known to be caused by defects in cholesterol metabolism, but support linking the malformation to abnormal hedgehog signaling has not definitively been made. Second, while in vitro studies have shown that proper levels of metabolic by-products of cholesterol are necessary for proper hedgehog signaling, our studies offer the strongest genetic animal model evidence to support this idea.

Mutations in the human SC4MOL gene encoding a methyl sterol oxidase cause psoriasiform dermatitis, microcephaly, and developmental delay

Defects in cholesterol synthesis result in a wide variety of symptoms, from neonatal lethality to the relatively mild dysmorphic features and developmental delay found in individuals with Smith-Lemli-Opitz syndrome. We report here the identification of mutations in sterol-C4-methyl oxidase–like gene (SC4MOL) as the cause of an autosomal recessive syndrome in a human patient with psoriasiform dermatitis, arthralgias, congenital cataracts, microcephaly, and developmental delay. This gene encodes a sterol-C4-methyl oxidase (SMO), which catalyzes demethylation of C4-methylsterols in the cholesterol synthesis pathway. C4-Methylsterols are meiosis-activating sterols (MASs). They exist at high concentrations in the testis and ovary and play roles in meiosis activation. In this study, we found that an accumulation of MASs in the patient led to cell overproliferation in both skin and blood. SMO deficiency also substantially altered immunocyte phenotype and in vitro function. MASs serve as ligands for liver X receptors α and β(LXRα and LXRβ), which are important in regulating not only lipid transport in the epidermis, but also innate and adaptive immunity. Deficiency of SMO represents a biochemical defect in the cholesterol synthesis pathway, the clinical spectrum of which remains to be defined.

Hypomorphic temperature-sensitive alleles of NSDHL cause CK syndrome

CK syndrome (CKS) is an X-linked recessive intellectual disability syndrome characterized by dysmorphism, cortical brain malformations, and an asthenic build. Through an X chromosome single-nucleotide variant scan in the first reported family, we identified linkage to a 5 Mb region on Xq28. Sequencing of this region detected a segregating 3 bp deletion (c.696_698del [p.Lys232del]) in exon 7 of NAD(P) dependent steroid dehydrogenase-like (NSDHL), a gene that encodes an enzyme in the cholesterol biosynthesis pathway. We also found that males with intellectual disability in another reported family with an NSDHL mutation (c.1098 dup [p.Arg367SerfsX33]) have CKS. These two mutations, which alter protein folding, show temperature-sensitive protein stability and complementation in Erg26-deficient yeast. As described for the allelic disorder CHILD syndrome, cells and cerebrospinal fluid from CKS patients have increased methyl sterol levels. We hypothesize that methyl sterol accumulation, not only cholesterol deficiency, causes CKS, given that cerebrospinal fluid cholesterol, plasma cholesterol, and plasma 24S-hydroxycholesterol levels are normal in males with CKS. In summary, CKS expands the spectrum of cholesterol-related disorders and insight into the role of cholesterol in human development.

A model of Costeff Syndrome reveals metabolic and protective functions of mitochondrial OPA3

Costeff Syndrome, which is caused by mutations in the OPTIC ATROPHY 3 (OPA3) gene, is an early-onset syndrome characterized by urinary excretion of 3-methylglutaconic acid (MGC), optic atrophy and movement disorders, including ataxia and extrapyramidal dysfunction. The OPA3 protein is enriched in the inner mitochondrial membrane and has mitochondrial targeting signals, but a requirement for mitochondrial localization has not been demonstrated. We find zebrafish opa3 mRNA to be expressed in the optic nerve and retinal layers, the counterparts of which in humans have high mitochondrial activity. Transcripts of zebrafish opa3 are also expressed in the embryonic brain, inner ear, heart, liver, intestine and swim bladder. We isolated a zebrafish opa3 null allele for which homozygous mutants display increased MGC levels, optic nerve deficits, ataxia and an extrapyramidal movement disorder. This correspondence of metabolic, ophthalmologic and movement abnormalities between humans and zebrafish demonstrates a phylogenetic conservation of OPA3 function. We also find that delivery of exogenous Opa3 can reduce increased MGC levels in opa3 mutants, and this reduction requires the mitochondrial localization signals of Opa3. By manipulating MGC precursor availability, we infer that elevated MGC in opa3 mutants derives from extra-mitochondrial HMG-CoA through a non-canonical pathway. The opa3 mutants have normal mitochondrial oxidative phosphorylation profiles, but are nonetheless sensitive to inhibitors of the electron transport chain, which supports clinical recommendations that individuals with Costeff Syndrome avoid mitochondria-damaging agents. In summary, this paper introduces a faithful Costeff Syndrome model and demonstrates a requirement for mitochondrial OPA3 to limit HMG-CoA-derived MGC and protect the electron transport chain against inhibitory compounds.

Clinical observations, molecular genetic analysis, and treatment of sitosterolemia in infants and children

The clinical observation and treatment of young children with sitosterolemia has rarely been reported. We report clinical, biochemical, and molecular genetic observations and treatment outcomes for five Chinese children from four separate families presenting with sitosterolemia in whom we identified two new (Y329X, G269R) and three known (R446X, N437K, R389H) mutations in the ABCG5 gene. The R389H mutation was found in 50% of alleles. Three of these five patients received cholestyramine therapy with a very good response. However, all patients discontinued this therapy because of poor compliance. Finally, all patients were on ezetimibe therapy and had satisfactory total serum cholesterol levels, though their plant sterol levels were still higher than normal. Another noteworthy finding is that a female infant had a serum cholesterol level of 654 mg/dl at 7 months of age, despite being breast fed (with very tiny amounts of plant sterols) since birth and undergoing 4 months of ezetimibe administration. Although she failed to respond to ezetimibe during this period, she did show improvement when the therapy was started again at 2 years of age. It is possible that another 23-month-old female patient also responded more slowly to ezetimibe treatment than older patients.

Abstract 5098: Targeting the cholesterol pathway gene SC4MOL sensitizes cancer to EGFR inhibitors

Epidermal growth factor receptor (EGFR) has been exploited as a target for blockade in cancer therapy, based on the known central role of EGFR signaling in promoting cancer cell growth. We have identified a novel mechanism for influencing EGFR activity that involves the sterol biosynthesis pathway enzyme sterol C4-methyl oxidase-like (SC4MOL). SC4MOL, in conjunction with other members of the ergosome complex (erg26/NSDHL; erg27/HSD17B7), catalyzes a non-redundant, irreversible step of demethylation at C4 of 14-demethylated lanosterol and dihydrolanosterol to produce zymosterol and 8(9)-cholestenol, respectively. Depletion of SC4MOL with siRNA caused accumulation of methylsterol intermediaries; inhibition of the key EGFR effectors, ERK and AKT; and a 3-fold increase in apoptosis specifically in the presence of EGFR antagonists. Metabolic block upstream of SC4MOL with ketoconazole or CYP51A1 siRNA eliminated methylsterols and completely reversed the effect of SC4MOL depletion, while added cholesterol did not rescue cancer cells from accelerated apoptosis upon concurrent SC4MOL and EGFR blockade. These results indicate that accumulation of specific cholesterol precursors enhances efficacy of anti-EGFR drugs. Further, we found that SC4MOL and the other ergosome components are transcriptionally regulated by EGFR signaling, suggesting involvement of C4 methylsterols in physiological activation of the EGFR signaling pathway.

A metabolic effect of sterol intermediaries on EGFR signaling has not been previously characterized. Such an effect could be exploited in cancer therapeutically by employing already existing drugs such as synthetic 4,4-dimethylsterols currently in use for in vitro fertilization.

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 5098.

Valproic acid prevents brain injury in a canine model of hypothermic circulatory arrest: a promising new approach to neuroprotection during cardiac surgery

BACKGROUND

The anticonvulsant valproic acid (sodium valproate, Depacon) acts as a neuroprotectant in rodents, but has never been tested in larger animals. We used valproate in our canine model of hypothermic circulatory arrest to evaluate its neuroprotective benefit in complex cardiac surgical cases.

METHODS

Thirteen dogs pretreated with valproate before 2 hours of hypothermic circulatory arrest survived for 24 hours (n = 7) or 72 hours (n = 6). Thirteen control animals (placebo only) also survived for 24 hours (n = 7) or 72 hours (n = 6) after hypothermic circulatory arrest. Blinded clinical neurologic evaluation was performed daily until sacrifice using the Pittsburgh Canine Neurologic Scoring System. Brains were harvested for blinded histopathologic analysis by a neuropathologist to determine the extent of apoptosis and necrosis in 11 brain regions (Total Brain Cell Death Score: 0 = normal, 99 = extensive neuronal death in all regions). Quantification of N-acetyl-aspartate, an established marker for brain injury, was performed with mass spectrometry.

RESULTS

Valproate dogs scored significantly better than control animals on clinical neurologic evaluation. Histopathologic examination revealed that valproate animals demonstrated less neuronal damage (by Total Brain Cell Death Score) than control animals at both 24 hours (16.4 versus 11.4; p = 0.03) and 72 hours (21.7 versus 17.7; p = 0.07). At 72 hours, the entorhinal cortex, an area involved with learning and memory, was significantly protected in valproate dogs (p < 0.05). Furthermore, the cortex, hippocampus, and cerebellum demonstrated preservation of near-normal N-acetyl-aspartate levels after valproate pretreatment.

CONCLUSIONS

These data demonstrate clinical, histologic, and biochemical improvements in dogs pretreated with valproate before hypothermic circulatory arrest. This commonly used drug may offer a promising new approach to neuroprotection during cardiac surgery.

Dehydrosteroid measurements in maternal urine or serum for the prenatal diagnosis of Smith–Lemli–Opitz syndrome (SLOS)

In a large multi-center trial involving prenatal screening for Smith-Lemli-Opitz syndrome (SLOS), we evaluated maternal urine and serum steroid analysis as a non-invasive diagnostic alternative to amniotic fluid sterol analysis. Candidate steroid ratios included: 7-dehydropregnanetriol/pregnanetriol (7-PT/PT), 8-dehydropregnanetriol/PT (8-PT/PT), the sum of these two (7 + 8-PT/PT), and dehydroestriol/estriol (DHE3/E3). Results are presented from 19 SLOS pregnancies, and 732 reference pregnancies that were screen positive for SLOS but negative on testing in amniotic fluid. Steroid ratios are expressed as multiples of the 75th centile (MoS), rather than multiples of the median, as most reference measurements were undetectable. All four urine ratios were available in 12 SLOS pregnancies; the median 7-PT/PT MoS was 94, with no overlap between affected and reference pregnancies in the second trimester. The separation between these groups increased by 27% per week. The other three ratios performed similarly in urine, with (7 + 8)-PT/PT ratios being marginally superior, due to fewer high reference outliers. All four steroid ratios in urine were diagnostic for SLOS between 14 and 22 weeks' gestation. In six SLOS pregnancies in which all serum analytes were measured, the median 7-PT/PT MoS was 71, and there was slight overlap in the second trimester. The separation increased by 28% per week. Steroid ratios in serum were less definitive than in urine but might be useful in certain circumstances, at 14 weeks gestation or later. Urine testing performance prior to 14 weeks gestation appears promising, but reference data are sparse.

Identifying Smith–Lemli–Opitz syndrome in conjunction with prenatal screening for Down syndrome

BACKGROUND

Smith-Lemli-Opitz syndrome (SLOS) is a rare hereditary disorder of cholesterol metabolism. We examine the feasibility of identifying SLOS as a part of a routine prenatal screening and evaluate diagnostic testing in maternal urine (or serum), in addition to amniotic fluid.

METHODS

Our SLOS risk algorithm utilized three Down syndrome screening markers (estimated 62% detection rate; 0.3% screen-positive rate). Fifteen North American prenatal screening programs implemented this algorithm.

RESULTS

SLOS risk was assigned to 1 079 301 pregnancies; 3083 were screen-positive (0.29%). Explanations were found for 1174, including 914 existing fetal deaths. Among the remaining pregnancies, 739 were screen-positive only for SLOS; 1170 were also screen-positive for other fetal disorders. Five of six SLOS pregnancies (83%) were screen-positive. All six had sonographic findings, were biochemically confirmed, and were terminated. Maternal urine steroid measurements were confirmatory in four cases tested. Second-trimester prevalence among Caucasians was 1 in 101 000 (1 in 130 000 overall; no cases in other racial groups). Among 739 pregnancies screen-positive only for SLOS, two cases were identified; another 69 had major fetal abnormalities.

CONCLUSIONS

Although SLOS occurred less often than previously reported, many other major abnormalities were detected. Implementing the algorithm as an adjunct to Down syndrome screening may be feasible.

Response of obligate heterozygotes for phytosterolemia to a low-fat diet and to a plant sterol ester dietary challenge

Twelve obligate heterozygotes from two kindreds were ascertained through phytosterolemic probands homozygous for molecular defects in the ATP binding cassette (ABC) half transporter, ABCG8. The response of these heterozygotes to a Step 1 diet low in fat, saturated fat, and cholesterol, and to 2.2 g daily of plant sterols (as esters) was determined in Protocol I (16 weeks) and Protocol II (28 weeks) during three consecutive feeding periods: Step 1/placebo spread; Step 1/plant sterol spread; and Step 1/placebo spread (washout). At baseline, half the heterozygotes had moderate dyslipidemia and one-third had mildly elevated campesterol and sitosterol levels. On the Step 1/placebo spread, mean LDL cholesterol decreased significantly, 11.2% in Protocol I (n = 12), and 16.0% in Protocol II (n = 7). Substitution with plant sterol spread produced a significant treatment effect on LDL levels in Protocols I and II. Conversely, the mean levels of campesterol and sitosterol increased 119% and 54%, respectively, during the use of plant sterol spread for 6 weeks in Protocol I, an effect mirrored for 12 weeks in Protocol II. During the placebo spread washouts, LDL levels increased, while those of plant sterols decreased to baseline levels in both protocols. In conclusion, phytosterolemic heterozygotes respond well to a Step 1 diet, and their response to a plant sterol ester challenge appears similar to that observed in normals.

Abnormal sterol metabolism in a patient with Antley-Bixler syndrome and ambiguous genitalia

Antley-Bixler syndrome (ABS) is a rare multiple anomaly syndrome comprising radiohumeral synostosis, bowed femora, fractures of the long bones, premature fusion of the calvarial sutures, severe midface hypoplasia, proptosis, choanal atresia, and, in some, ambiguous genitalia. Of fewer than 40 patients described to date, most have been sporadic, although reports of parental consanguinity and affected sibs of both sexes suggests autosomal recessive inheritance in some families. Known genetic causes among sporadic cases of ABS or ABS-like syndromes are missense mutations in the IgII and IgIII regions of FGFR2, although the assignment of the diagnosis of ABS to such children has been disputed. A third cause of an ABS-like phenotype is early in utero exposure to fluconazole, an inhibitor of lanosterol 14-alpha-demethylase. The fourth proposed cause of ABS is digenic inheritance combining heterozygosity or homozygosity for steroid 21-hydroxylase deficiency with effects from a second gene at an unknown locus. Because fluconazole is a strong inhibitor of lanosterol 14-alpha-demethylase (CYP51), we evaluated sterol metabolism in lymphoblast cell lines from an ABS patient without a known FGFR2 mutation and from a patient with an FGFR2 mutation and ABS-like manifestations. When grown in the absence of cholesterol to stimulate cholesterol biosynthesis, the cells from the ABS patient with ambiguous genitalia but without an FGFR2 mutation accumulated markedly increased levels of lanosterol and dihydrolanosterol. Although the abnormal sterol profile suggested a deficiency of lanosterol 14-alpha-demethylase, mutational analysis of its gene, CYP51, disclosed no obvious pathogenic mutation in any of its 10 exons or exon-intron boundaries. Sterol metabolism in lymphoblasts from the phenotypically unaffected mother was normal. Our results suggest that ABS can occur in a patient with an intrinsic defect of cholesterol biosynthesis at the level of lanosterol 14-alpha-demethylase, although the genetic nature of the deficiency remains to be determined.

Lethal form of chondrodysplasia punctata with normal plasmalogen and cholesterol biosynthesis

We present a male autopsied case of chondrodysplasia punctata with abnormal face, symmetrical proximal limb shortness, severe psychomotor developmental delay, respiratory muscle weakness, and death at the age of 2 years. Although his clinical manifestations were similar to those of rhizomelic chondrodysplasia punctata (RCDP), biochemical studies using skin fibroblasts did not document the peroxisomal dysfunction described in RCDP. In addition, the sterol profile, for which abnormalities have recently been reported in cases of X-linked dominant form chondrodysplasia punctata (CDPX2), was normal both in the liver and in the fibroblasts. This patient may represent a new lethal form of chondrodysplasia punctata.

Difficult prenatal diagnosis in mild Smith-Lemli-Opitz syndrome

Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive disorder of cholesterol biosynthesis caused by mutations of the 7-dehydrocholesterol (7DHC) reductase gene (DHCR7). We present our experience with prenatal diagnosis of an affected fetus with a very mild form of SLOS. The mother underwent prenatal diagnosis by chorionic villus (CV) sampling at 11 2/7 weeks because of having two prior affected sons with SLOS. The 7DHC/total-sterol ratio in the fetus was higher than in normal control fetuses but lower than the ratio observed in CV of three other fetuses in whom SLOS was diagnosed prenatally. The pregnancy was terminated at 13 2/7 weeks. The level of 7DHC in amniotic fluid (AF) obtained at the time of pregnancy termination was unequivocally elevated, confirming the diagnosis of SLOS. This report illustrates the difficulties with the interpretation of biochemical prenatal diagnosis based on the determination of 7DHC/total-sterol ratio in CV sample in a case of mild SLOS, whereas biochemical testing of amniotic fluid clearly manifests the biochemical defects of SLOS as early as 13 weeks of gestation.

CHILD syndrome caused by deficiency of 3beta-hydroxysteroid-delta8, delta7-isomerase

CHILD (congenital hemidysplasia, ichthyosis, and limb defects) syndrome is a rare, usually sporadic disorder associated with unilateral distribution of ichthyosiform skin lesions, limb defects, punctate calcifications of cartilaginous structures, and visceral anomalies. CHILD syndrome shares some manifestations with X-linked dominant Conradi-Hünermann syndrome (CDPX2), although the skeletal defects and skin lesions in CDPX2 are bilateral and asymmetric. Because CDPX2 patients have abnormal 8-dehydrosterol metabolism caused by mutations in 3beta-hydroxysteroid-delta8,delta7-isomerase, we measured plasma sterols in a patient with CHILD syndrome and found levels of 8-dehydrocholesterol and 8(9)-cholestenol increased to the same degree as in CDPX2 patients. Subsequently, we identified a nonsense mutation in exon 3 of the patient's 3beta-hydroxysteroid-delta8,delta7-isomerase gene. We speculate that at least some cases of CHILD syndrome are allelic with CDPX2 caused by 3beta-hydroxysteroid-delta8,delta7-isomerase deficiency.

Midgestational maternal urine steroid markers of fetal Smith-Lemli-Opitz (SLO) syndrome (7-dehydrocholesterol 7-reductase deficiency)

Smith-Lemli-Opitz syndrome (SLOS) is a malformation syndrome associated with 7-dehydrocholesterol (7DHC) 7-reductase deficiency. Although SLOS can be detected in an affected fetus before midpregnancy by measurement of 7DHC levels in amniotic fluid or chorionic villus cells, a noninvasive, more routine method is needed. Accordingly, this study was instigated to search for specific steroids in maternal urine in an affected pregnancy that reflect the 7-reductase deficiency of the fetus, ie, steroids retaining 7,8-unsaturation. Steroids were characterized by gas chromatography/mass spectrometry after urinary extraction, conjugate separation, and derivatization. Most steroids in maternal urine from a patient carrying a SLOS fetus were identified as progesterone metabolites, and these were entirely conventional, showing no evidence of additional unsaturation. Unsaturated homologues of the cortisol metabolites were also not detected. However, unsaturated homologues of pregnane-3,16,20-triols and pregnane-3,17,20-triol were found. Most likely, these are 7,8-unsaturated homologues, but 8,9-unsaturation is also possible because of the known activity of delta7-delta8-isomerase on 7DHC, which results in 8DHC being a prominent sterol in SLOS. Among these novel human steroids, the following were provisionally characterized: 5beta-pregn-7(or 8)-ene-3alpha,17alpha,20alpha-triol, 5beta-pregn-7(or 8)-ene-3alpha,16alpha,20alpha-triol, and 5alpha-pregn-7(or 8)-ene-3,16alpha,20alpha-triol. Confirmation of the position of unsaturation will require steroid synthesis. These novel steroids are not present in normal pregnancy urine and, therefore, are valuable for prenatal diagnosis of SLOS. In addition, separate studies have shown that 5beta-pregn-7(or 8)-ene-3alpha,17alpha,20alpha-triol is present in urine of children and adults with SLOS, and so is a useful analyte for confirmation of the disorder throughout life.

Abnormal sterol metabolism in patients with Conradi-Hünermann-Happle syndrome and sporadic lethal chondrodysplasia punctata

The term, "chondrodysplasia punctata" (CDP) denotes a pattern of abnormal punctate calcification of dystrophic epiphyseal cartilage and certain other cartilaginous structures, such as the larynx. CDP occurs in a variety of genetic disorders associated with skeletal dwarfism and can also be caused by prenatal exposure to warfarin. Although the most studied clinical syndrome with CDP, rhizomelic chondrodysplasia punctata (RCDP), is known to be caused by several different abnormalities of plasmalogen biosynthesis, there are many other genetic disorders with CDP for which the biochemical cause is unknown. Because patients with Smith-Lemli-Opitz syndrome, a primary disorder of sterol biosynthesis, often have rhizomesomelic limb shortness and, less commonly, CDP, we assessed sterol levels and metabolism in patients with different clinical forms of CDP. By quantitative sterol analysis of a variety of tissues, we identified 5 patients with similar radiological findings and abnormally increased levels of 8-dehydrocholesterol and cholest-8(9)-en-3beta-ol, suggesting a deficiency of 3beta-hydroxysteroid-delta8,delta7-isomerase, a principal enzyme of cholesterol biosynthesis. Cultured cells available from one patient showed increased levels of the same two sterols, decreased synthesis of cholesterol, and a pattern of inhibition by triparanol and AY-9944 consistent with a deficiency of 3beta-hydroxysteroid-delta8,delta7-isomerase. Clinical diagnoses among the 5 patients included X-linked dominant Conradi-Hünermann-Happle syndrome and nonspecific lethal CDP. We conclude that abnormal cholesterol biosynthesis is a characteristic of some clinical syndromes with rhizomesomelic dwarfing and CDP.

Equine type estrogens produced by a pregnant woman carrying a Smith-Lemli-Opitz syndrome fetus

The equine-type estriols 1,3,5(10),7-estratetraene-3,16alpha,17beta-triol (16alpha-hydroxy-17beta-dihydroequilin) and 1,3,5(10),6,8-estrapentaene-3,16alpha,17beta-triol (16alpha-hydroxy-17beta-dihydroequilenin) constituted over half of the estrogens excreted by a woman carrying a Smith-Lemli-Opitz syndrome (SLOS) affected fetus. The steroids were characterized by gas chromatography-mass spectrometry (GC/MS), and mass spectra of the dehydro estriols as trimethylsilyl ethers are illustrated. SLOS is associated with 7-dehydrocholesterol (7DHC), delta 7-reductase deficiency; the enzyme catalyzing the final step in cholesterol biosynthesis. Identification of these equine estrogens show that an estrogen biosynthetic pathway parallel to normal is functional in the feto-placental unit and uses 7DHC as precursor, therefore P450scc, P450c17, and 3betaHSD and P450arom are all active on 7-dehydrometabolites. Patients with affected fetuses have low plasma estriol values (probably due to deficient production of the cholesterol precursor) and this is often a warning sign which instigates further evaluation for SLOS. The estriol deficiency is not quantitatively made up by the dehydrometabolites, and the combined excretion was found to be about one-third of the mean of gestational age matched controls. The importance of these findings lies in the potential value of dehydroestriol measurement for non-invasive diagnosis of SLOS at mid-gestation. Currently diagnosis relies on imaging, since SLOS is a malformation syndrome, and measurement of 7DHC levels in amniotic fluid and chorionic villus tissue.

Prenatal diagnosis of the RSH/Smith-Lemli-Opitz syndrome

The RSH/Smith-Lemli-Opitz syndrome (RSH/SLOS) is a relatively common, autosomal recessive malformation syndrome comprising distinctive facial, limb and genital anomalies, and mental retardation. Most patients with a clinical diagnosis of RSH/SLOS have a defect of cholesterol biosynthesis at the level of 3beta-hydroxysteroid-delta7-reductase, resulting in a decreased level of cholesterol and an increased level of 7-dehydrocholesterol (7DHC) in body fluids and tissues. We report on our experience with the prenatal diagnosis of RSH/SLOS by quantitative sterol chromatography in amniotic fluid (AF) and chorionic villus (CV). Of 76 AF and nine CV samples analyzed for various indications, 20 were diagnostic of RSH/SLOS based on an increased level of 7DHC in the fluid or tissue. Of 39 fetuses at a 25% risk for RSH/SLOS, 10(25.6%) were affected. Twenty-nine pregnancies not known to be at risk for RSH/SLOS were studied because of either a fetal abnormality characteristic of RSH/SLOS detected by ultrasound, a low maternal serum uE3 level (MSuE3), or both. None of the pregnancies tested, because of a low MSuE3 but lacking a sonographic abnormality characteristic of RSH/SLOS, was affected. However, three of four pregnancies with a low MSuE3 and an RSH/SLOS-type fetal abnormality were positive. RSH/ SLOS was diagnosed in two additional pregnancies on which MSuE3 data were not available but in which fetal anomalies were identified. Of these five RSH/SLOS fetuses identified in pregnancies not otherwise at risk for RSH/SLOS, the presenting sonographic anomaly was either polydactyly, ambiguous genitalia, or both. Evaluation of the biochemical parameters and clinical severity of RSH/SLOS showed that there was an inverse correlation between clinical severity and both the level of AF 7DHC and the level of MSuE3. Based on these earlier and more extensive studies, we conclude that accurate prenatal diagnosis of RSH/ SLOS is possible by sterol analysis of AF and, most likely, CV specimens as well. Furthermore, our findings suggest that MSuE3 levels in combination with sonography may provide useful diagnostic and prognostic information in the absence of a family history of RSH/SLOS.

Clinical and biochemical spectrum of patients with RSH/Smith-Lemli-Opitz syndrome and abnormal cholesterol metabolism

RSH/Smith-Lemli-Opitz (RSH/SLO) syndrome is an autosomal recessive malformation syndrome recently shown to be associated with a severe deficiency of cholesterol biosynthesis and markedly elevated plasma and tissue levels of 7-dehydrocholesterol (7-DHC), the immediate precursor of cholesterol in the Kandutsch-Russell biosynthetic pathway. Because these biochemical abnormalities permit a reassessment of RSH/SLO on biochemical criteria rather than less specific physical criteria, we review here the clinical and biochemical characteristics of our first 80 patients with abnormally increased levels of 7-DHC. The study population included 68 index patients and 12 additional relatives identified by quantification of 7-DHC and cholesterol in plasma, amniotic fluid, or cultured fibroblasts, lymphoblasts, or amniocytes. As demonstrated in other clinical syndromes when redefined biochemically, we have found a wider range of clinical expression of RSH/SLO than previously recognized. These newly recognized atypical RSH/SLO patients included several with no malformations other than syndactyly of the toes and, at the other extreme, patients with frank holoprosencephaly or multiple visceral anomalies who died in utero. Syndactyly of toes 2 and 3 was the most common malformation, occurring in all but one of 80 patients. The best biochemical predictor of clinical severity was the plasma cholesterol level, which decreased with increasing clinical severity. However, at least 10% of patients, including one newborn infant, had normal cholesterol levels at the time of diagnosis and would have been missed without specific quantification of 7-DHC. Not unexpectedly, several patients carrying a clinical diagnosis of RSH/SLO were found to have normal levels of all plasma sterols and apparently normal cholesterol biosynthesis in cultured cells. A comparison of the frequency of anomalies in our biochemically identified patients with similar data from previously reported clinical series suggests that up to 25% of reports of RSH/SLO in the literature may describe genetic conditions other than RSH/SLO with 7-DHC-emia.

Cloning of glutaryl-CoA dehydrogenase cDNA, and expression of wild type and mutant enzymes in Escherichia coli

We have cloned, sequenced, and expressed cDNAs encoding wild type human glutaryl-CoA dehydrogenase subunit, and have expressed a mutant enzyme found in a patient with glutaric acidemia type I. The mutant protein is expressed at the same level as the wild type in Escherichia coli, but has less than 1% of the activity of wild-type dehydrogenase. We also present evidence that the glutaryl-CoA dehydrogenase transcript is alternatively spliced in human fibroblasts and liver; the alternatively spliced mRNA, when expressed in E.coli, encodes a stable but inactive protein. Purified expressed human glutaryl-CoA dehydrogenase has kinetic constants similar to those of the previously purified porcine dehydrogenase. The primary translation product from in vitro transcribed glutaryl-CoA dehydrogenase mRNA is translocated into mitochondria and processed in the same manner as most other nuclear-encoded mitochondrial proteins. Human glutaryl-CoA dehydrogenase shows 53% sequence similarity to porcine medium chain acyl-CoA dehydrogenase, and these similarities were utilized to predict structure-function relationships in glutaryl-CoA dehydrogenase.

Short-term response to dietary therapy in molybdenum cofactor deficiency

Molybdenum cofactor deficiency was diagnosed in a 3-month-old girl who presented with microcephaly, developmental delay, severe irritability, and lactic acidosis. Dietary methionine restriction, with cysteine supplementation, was associated with moderate short-term clinical improvement, including a resumption in predicted head growth, modest developmental progress, and a reduction in irritability. Clinical relapse was associated with noncompliance of dietary therapy 2 months later. Urinary sulfite levels measured by commercial dipsticks were useful in following therapy. Molybdenum cofactor deficiency is probably frequently underdiagnosed due to the lack of specific clinical or laboratory features. Screening of infants at risk for the presence of urinary sulfites or serum hypouricemia, or both, is both rapid and inexpensive.

Association of scleroderma with a T cell antigen receptor gamma gene restriction fragment length polymorphism

Restriction fragment length polymorphisms (RFLPs) in the T cell receptor (TCR) alpha, beta, and gamma genes were analyzed in 61 scleroderma patients and 150 controls. An association was found between scleroderma and an 11.3-kb Pvu II fragment in the TCR gamma gene; this gene was found in 41.0% of the patients, compared with 21.7% of the controls (P less than 0.01, odds ratio = 2.50). There were no associations between scleroderma and the tested RFLPs in the TCR alpha or beta genes, and no RFLPs were found in the constant region of the TCR delta gene.

Lack of association between scleroderma and types I and III procollagen gene restriction fragment length polymorphisms

Restriction fragment length polymorphisms (RFLPs) in types I and III procollagen genes were studied in 62 scleroderma patients and 138 healthy controls. Allelic frequencies were determined for each RFLP, and comparisons were made between the 2 populations, stratifying them by race when appropriate. No statistically significant differences were observed for the frequencies of any of the RFLPs studied.

Lack of an association between diffuse systemic sclerosis and HLA-DR1 or HLA-DR5

The HLA-DR locus of the major histocompatibility complex encodes class II molecules which participate in immune responses through regulation of T cell interaction with antigen presenting cells. Previous association studies between HLA-DR antigens and the autoimmune disease, systemic sclerosis (or scleroderma), have yielded conflicting results. Some investigators have reported an association between this disease and HLA-DR1, while others have demonstrated an association with HLA-DR5. In this study, we used restriction fragment length polymorphisms in the HLA-DR locus to compare allelic frequencies of HLA-DR1 and HLA-DR5 in scleroderma patients with diffuse disease and healthy control subjects. No significant difference in the allelic frequency of either antigen was observed between the groups. These results suggest that HLA-DR1 and HLA-DR5 antigens are unlikely to contribute significantly to disease susceptibility in scleroderma.

A comparison of in vivo and in vitro metabolites of the H1-antagonist N,N-dimethyl-N'-2-pyridyl-N'-(2-thienylmethyl)-1,2-ethanediamine (methapyrilene) in the rat

1. The H1-antagonist N,N-dimethyl-N'-2-pyridyl-N'-(2-thienylmethyl)-1,2-ethanediamine (methapyrilene) is carcinogenic in rats. 2. The compound, which is inactive in short-term tests and does not bind to DNA, has been classified as a non-genotoxic carcinogen. 3. Studies have been made in vitro and in vivo in F344 and Sprague-Dawley rats. New metabolites included N-(N',N'-dimethylaminoethyl)-2-aminopyridine and the corresponding N'-oxide, a derivative in which methapyrilene is hydroxylated on the 5-position of the pyridine ring, 2-(N',N'-dimethylamino)-N-2'-pyridylacetamide, N-(2-pyridyl)-N-2"-thienylmethyl)aminoacetaldehyde, and 2-hydroxymethylthiophene. 4. Both strains of rat metabolize methapyrilene to reactive species which may be of importance in the carcinogenic process.