A rare case of sterol-C4-methyl oxidase deficiency in a young Italian male: Biochemical and molecular characterization

Defects in CYB5A and CYB5B impact sterol-C4 oxidation in cholesterol biosynthesis and demonstrate regulatory roles of dimethyl sterols

Cytochrome b5 (CYB5) is a hemoprotein crucial for electron transfer to oxygenases. Although microsomal CYB5A is required for sterol C4-demethylation in vitro, cholesterol biosynthesis remains intact in Cyb5a knockout mice. Here, we show that knockout of mitochondrial CYB5B, rather than CYB5A, blocks cholesterol biosynthesis at the sterol-C4 oxidation step in HeLa cells, causing an accumulation of testis meiosis-activating sterol (T-MAS) and dihydro-T-MAS. Surprisingly, liver-specific Cyb5b knockout (L-Cyb5b-/-) mice exhibit normal cholesterol metabolism. Further knockdown of Cyb5a in L-Cyb5b-/- (L-Cyb5b-/-/short hairpin [sh]Cyb5a) mice leads to a marked accumulation of T-MAS and dihydro-T-MAS, indicating that either CYB5A or CYB5B is required for sterol C4-demethylation. The L-Cyb5b-/-/shCyb5a mice are largely normal, with lower sterol regulatory element-binding protein (SREBP)-target gene expression during refeeding and higher liver triglyceride levels while fasting, as T-MAS and dihydro-T-MAS inhibit the SREBP pathway and activate the PPARγ pathway. In summary, CYB5A and CYB5B compensate for sterol C4-demethylation, and T-MAS and dihydro-T-MAS can modulate the SREBP and PPARγ pathways.

Evaluation of Antifungal Selective Toxicity Using Candida glabrata ERG25 and Human SC4MOL Knock-In Strains

With only four classes of antifungal drugs available for the treatment of invasive systemic fungal infections, the number of resistant fungi is increasing, highlighting the urgent need for novel antifungal drugs. Ergosterol, an essential component of cell membranes, and its synthetic pathway have been targeted for antifungal drug development. Sterol-C4-methyl monooxygenase (Erg25p), which is a greater essential target than that of existing drugs, represents a promising drug target. However, the development of antifungal drugs must consider potential side effects, emphasizing the importance of evaluating their selective toxicity against fungi. In this study, we knocked in ERG25 of Candida glabrata and its human ortholog, SC4MOL, in ERG25-deleted Saccharomyces cerevisiae. Utilizing these strains, we evaluated 1181-0519, an Erg25p inhibitor, that exhibited selective toxicity against the C. glabrata ERG25 knock-in strain. Furthermore, 1181-0519 demonstrated broad-spectrum antifungal activity against pathogenic Candida species, including Candida auris. The approach of utilizing a gene that is functionally conserved between yeast and humans and subsequently screening for molecular target drugs enables the identification of selective inhibitors for both species.

MSMO1 deficiency: a potentially partially treatable, ultrarare neurodevelopmental disorder with psoriasiform dermatitis, alopecia and polydactyly

MSMO1 deficiency (OMIM #616834) is an ultrarare autosomal recessive disorder of distal cholesterol metabolism with only five cases reported to date. The disorder is caused by missense variants in the MSMO1 gene encoding methylsterol monooxygenase 1, leading to the accumulation of methylsterols. Clinically, MSMO1 deficiency is characterized by growth and developmental delay, often in association with congenital cataracts, microcephaly, psoriasiform dermatitis and immune dysfunction. Treatment with oral and topical cholesterol supplements and statins was reported to improve the biochemical, immunological, and cutaneous findings, supporting a potential treatment following the precision diagnosis of MSMO1 deficiency. We describe two siblings from a consanguineous family presenting with novel clinical features of polydactyly, alopecia and spasticity. Whole-exome sequencing revealed a novel, homozygous c.548A > C, p.(Glu183Ala) variant. Based on previously published treatment algorithms, we initiated a modified dosage regime with systemic cholesterol supplementation, statins and bile acid along with topical application of a cholesterol/statin formulation. This resulted in a marked improvement of psoriasiform dermatitis and some hair growth.

New Homozygous Missense MSMO1 Mutation in Two Siblings with SC4MOL Deficiency Presenting with Psoriasiform Dermatitis

Sterol-C4-methyl oxidase (SC4MOL) deficiency was recently described as an autosomal recessive cholesterol biosynthesis disorder caused by mutations in the MSMO1 (sometimes also referred to as SC4MOL) gene. To date, 5 patients from 4 unrelated families with SC4MOL deficiency have been reported. Diagnosis can be challenging as the biochemical accumulation of methylsterols can affect global development and cause skin and ocular pathology. Herein, we describe 2 siblings from a consanguineous Turkish family with SC4MOL deficiency presenting with psoriasiform dermatitis, ocular abnormalities (nystagmus, optic hypoplasia, myopia, and strabismus), severe intellectual disability, and growth and motor delay. We undertook whole-exome sequencing and identified a new homozygous missense mutation c.81A>C; p.Asn27Thr in MSMO1. Segregation analysis in all available family members confirmed recessive inheritance of the mutation. The siblings were treated with a combination of oral and topical statin and cholesterol which resulted in clinical improvement. This study demonstrates how genomics-based diagnosis and therapy can be helpful in clinical practice.

Zebrafish models of skeletal dysplasia induced by cholesterol biosynthesis deficiency

Human disorders of the post-squalene cholesterol biosynthesis pathway frequently result in skeletal abnormalities, yet our understanding of the mechanisms involved is limited. In a forward-genetic approach, we have found that a late-onset skeletal mutant, named kolibernu7 , is the result of a cis-acting regulatory mutation leading to loss of methylsterol monooxygenase 1 (msmo1) expression within pre-hypertrophic chondrocytes. Generated msmo1nu81 knockdown mutation resulted in lethality at larval stage. We demonstrated that this is a result of both cholesterol deprivation and sterol intermediate accumulation by creating a mutation eliminating activity of Lanosterol synthase (Lss). Our results indicate that double lssnu60;msmo1nu81 and single lssnu60 mutants survive significantly longer than msmo1nu81 homozygotes. Liver-specific restoration of either Msmo1 or Lss in corresponding mutant backgrounds suppresses larval lethality. Rescued mutants develop dramatic skeletal abnormalities, with a loss of Msmo1 activity resulting in a more-severe patterning defect of a near-complete loss of hypertrophic chondrocytes marked by col10a1a expression. Our analysis suggests that hypertrophic chondrocytes depend on endogenous cholesterol synthesis, and blocking C4 demethylation exacerbates the cholesterol deficiency phenotype. Our findings offer new insight into the genetic control of bone development and provide new zebrafish models for human disorders of the cholesterol biosynthesis pathway.

RNA Sequencing-Based Whole-Transcriptome Analysis of Friesian Cattle Fed with Grape Pomace-Supplemented Diet

Simple Summary

Grape pomace (GPO) is an important source of polyphenols which are known to have antioxidant properties. In the past decade, GPO has received some attention as a bioactive dietary component in farm animals’ diet. In this study, we have analyzed the whole-transcriptome of Friesian calves fed with a GPO-supplemented diet using RNA-sequencing. We noted that the most affected pathway was the cholesterol lipid biosynthesis and this effect was consistent with a reduction in both serum cholesterol and lipid oxidation in the carcasses. This study provides evidence on the antioxidant property of GPO-supplemented diet, from a molecular biology standpoint.

Abstract

Grape pomace (GPO), the main by-product of the wine making process, is a rich source of polyphenols with potent antioxidant properties. Recently, GPO has emerged as a potential feed additive in livestock nutrition, with several reports describing its beneficial effects on animals’ overall health status or production traits. However, little is known about it from a molecular biology standpoint. In the present study, we report the first RNA sequencing-based whole-transcriptome profiling of Friesian calves fed with a GPO-supplemented diet. We identified 367 differentially expressed genes (p < 0.05) in the GPO-supplemented calves (n = 5), when compared with unsupplemented control group (n = 5). The pathway analysis showed that ‘cholesterol lipid biosynthesis’ was the most negatively-enriched (p < 0.001) pathway in the GPO-supplemented animals. In specific terms, five important genes coding for cholesterol biosynthesis enzymes, namely the Farnesyl-diphosphate Farnesyltransferase 1 (FDFT-1), Squalene Epoxidase (SQLE), NAD(P)-dependent Steroid Dehydrogenase-like (NSDHL), Methylsterol Monooxygenase (MSMO)-1, and Sterol-C5-desaturase (SC5D), two major transcription factors (the Sterol Regulatory Element-binding Transcription Factor 1 and 2), as well as the Low-Density Lipoprotein Receptor (LDLR), were all downregulated following GPO supplementation. Such an effect was mirrored by a reduction of blood cholesterol levels (p = 0.07) and a lowered (p < 0.001) Malondialdehyde (lipid oxidation marker) level in carcasses. We provide evidence on the effects of GPO-supplemented diets on the whole-transcriptome signature in veal calves, which mainly reflects an antioxidant activity.

Liver and the defects of cholesterol and bile acids biosynthesis: Rare disorders many diagnostic pitfalls

In recent decades, biotechnology produced a growth of knowledge on the causes and mechanisms of metabolic diseases that have formed the basis for their study, diagnosis and treatment. Unfortunately, it is well known that the clinical features of metabolic diseases can manifest themselves with very different characteristics and escape early detection. Also, it is well known that the prognosis of many metabolic diseases is excellent if diagnosed and treated early. In this editorial we briefly summarized two groups of inherited metabolic diseases, the defects of cholesterol biosynthesis and those of bile acids. Both groups show variable clinical manifestations but some clinical signs and symptoms are common in both the defects of cholesterol and bile acids. The differential diagnosis can be made analyzing sterol profiles in blood and/or bile acids in blood and urine by chromatographic techniques (GC-MS and LC-MS/MS). Several defects of both biosynthetic pathways are treatable so early diagnosis is crucial. Unfortunately their diagnosis is made too late, due either to the clinical heterogeneity of the syndromes (severe, mild and very mild) that to the scarcity of scientific dissemination of these rare diseases. Therefore, the delay in diagnosis leads the patient to the medical observation when the disease has produced irreversible damages to the body. Here, we highlighted simple clinical and laboratory descriptions that can potentially make you to suspect a defect in cholesterol biosynthesis and/or bile acids, as well, we suggest appropriate request of the laboratory tests that along with common clinical features can help to diagnose these defects.