A retrospective analysis of endocrine disease in sphingosine-1-phosphate lyase insufficiency: case series and literature review

Primary adrenal insufficiency; Primary hypothyroidism; Sphingosine-1-phosphate lyaseInsuficiencia suprarrenal primaria; Hipotiroidismo primario; Esfingosina-1-fosfato liasaInsuficiència suprarenal primària; Hipotiroïdisme primari; Esfingosina-1-fosfat liasaSphingosine-1-phosphate lyase (SGPL1) insufficiency syndrome (SPLIS) is an autosomal recessive multi-system disorder, which mainly incorporates steroid-resistant nephrotic syndrome and primary adrenal insufficiency. Other variable endocrine manifestations are described. In this study, we aimed to comprehensively annotate the endocrinopathies associated with pathogenic SGPL1 variants and assess for genotype–phenotype correlations by retrospectively reviewing the reports of endocrine disease within our patient cohort and all published cases in the wider literature up to February 2022. Glucocorticoid insufficiency in early childhood is the most common endocrine manifestation affecting 64% of the 50 patients reported with SPLIS, and a third of these individuals have additional mineralocorticoid deficiency. While most individuals also have nephrotic syndrome, SGPL1 variants also account for isolated adrenal insufficiency at presentation. Primary gonadal insufficiency, manifesting with microphallus and cryptorchidism, is reported in less than one-third of affected boys, all with concomitant adrenal disease. Mild primary hypothyroidism affects approximately a third of patients. There is paucity of data on the impact of SGPL1 deficiency on growth, and pubertal development, limited by the early and high mortality rate (approximately 50%). There is no clear genotype–phenotype correlation overall in the syndrome, with variable disease penetrance within individual kindreds. However, with regards to endocrine phenotype, the most prevalent disease variant p.R222Q (affecting 22%) is most consistently associated with isolated glucocorticoid deficiency.To conclude, SPLIS is associated with significant multiple endocrine disorders. While endocrinopathy in the syndrome generally presents in infancy, late-onset disease also occurs. Screening for these is therefore warranted both at diagnosis and through follow-up.This work was supported by the Medical Research Council (MRC) UK Clinical Academic Research Partner Grant (MR/T02402X/1, 2019 to R P), Barts and the London Charity (MGU0361, 2017 to L A M), Barts and the London Charity Research Fellow Grant (MGU0528 to R K), Medical Research Council (MRC) UK Clinical Research Training Fellowship Grant (MR/W015935/1 to RK), Government of Trinidad and Tobago Research Fellowship (to A M) and Wellcome Trust (209328/Z/17/Z to J C A)

A retrospective analysis of endocrine disease in sphingosine-1-phosphate lyase insufficiency: case series and literature review

Sphingosine-1-phosphate lyase (SGPL1) insufficiency syndrome (SPLIS) is an autosomal recessive multi-system disorder, which mainly incorporates steroid-resistant nephrotic syndrome and primary adrenal insufficiency. Other variable endocrine manifestations are described. In this study, we aimed to comprehensively annotate the endocrinopathies associated with pathogenic SGPL1 variants and assess for genotype–phenotype correlations by retrospectively reviewing the reports of endocrine disease within our patient cohort and all published cases in the wider literature up to February 2022. Glucocorticoid insufficiency in early childhood is the most common endocrine manifestation affecting 64% of the 50 patients reported with SPLIS, and a third of these individuals have additional mineralocorticoid deficiency. While most individuals also have nephrotic syndrome, SGPL1 variants also account for isolated adrenal insufficiency at presentation. Primary gonadal insufficiency, manifesting with microphallus and cryptorchidism, is reported in less than one-third of affected boys, all with concomitant adrenal disease. Mild primary hypothyroidism affects approximately a third of patients. There is paucity of data on the impact of SGPL1 deficiency on growth, and pubertal development, limited by the early and high mortality rate (approximately 50%). There is no clear genotype–phenotype correlation overall in the syndrome, with variable disease penetrance within individual kindreds. However, with regards to endocrine phenotype, the most prevalent disease variant p.R222Q (affecting 22%) is most consistently associated with isolated glucocorticoid deficiency. To conclude, SPLIS is associated with significant multiple endocrine disorders. While endocrinopathy in the syndrome generally presents in infancy, late-onset disease also occurs. Screening for these is therefore warranted both at diagnosis and through follow-up

Sphingosine-1-phosphate lyase mutations cause primary adrenal insufficiency and steroid-resistant nephrotic syndrome

Primary adrenal insufficiency is life threatening and can present alone or in combination with other comorbidities. Here, we have described a primary adrenal insufficiency syndrome and steroid-resistant nephrotic syndrome caused by loss-of-function mutations in sphingosine-1-phosphate lyase (SGPL1). SGPL1 executes the final decisive step of the sphingolipid breakdown pathway, mediating the irreversible cleavage of the lipid-signaling molecule sphingosine-1-phosphate (S1P). Mutations in other upstream components of the pathway lead to harmful accumulation of lysosomal sphingolipid species, which are associated with a series of conditions known as the sphingolipidoses. In this work, we have identified 4 different homozygous mutations, c.665G>A (p.R222Q), c.1633_1635delTTC (p.F545del), c.261+1G>A (p.S65Rfs*6), and c.7dupA (p.S3Kfs*11), in 5 families with the condition. In total, 8 patients were investigated, some of whom also manifested other features, including ichthyosis, primary hypothyroidism, neurological symptoms, and cryptorchidism. Sgpl1-/- mice recapitulated the main characteristics of the human disease with abnormal adrenal and renal morphology. Sgpl1-/- mice displayed disrupted adrenocortical zonation and defective expression of steroidogenic enzymes as well as renal histology in keeping with a glomerular phenotype. In summary, we have identified SGPL1 mutations in humans that perhaps represent a distinct multisystemic disorder of sphingolipid metabolism

Investigating the Role of Sphingolipids in Steroidgenesis and Adrenal Disease.

PhD Theses. MedicalSphingosine-1-phosphate lyase insufficiency syndrome (SPLIS) due to loss of function mutations in SGPL1, is a multi-systemic disorder characterized by primary adrenal insufficiency, steroid resistant nephrotic syndrome and several extra adrenal manifestations including primary hypothyroidism, primary gonadal failure, ichthyosis, neurodevelopmental delay, lymphopenia and dyslipidaemia. Mass spectrometric analysis of plasma sphingolipids in several patients revealed elevated sphingosine-1-phosphate and ceramide levels when compared to age and sex matched controls suggesting that the underlying pathology in these patients may be due to cytosolic accumulation of specific sphingolipid intermediates. There is however, no evident genotype-phenotype correlation in SPLIS, with equally severe clinical phenotypes seen in mutations outside the active region and in both frameshift and missense mutations. Given that mitochondrial perturbations have been widely reported in lysosomal storage diseases with an almost reciprocal relationship between both organelles1,2 and the crucial involvement of mitochondria to the steroidogenic process, dysregulated mitochondrial dynamics was hypothesized to account for the steroidogenic biosynthetic defect linked to S1P lyase deficiency. Assessment of the impact of SGPL1 ablation on mitochondrial morphology and function was investigated using patient derived dermal fibroblasts and an isogenic CRISPR-Cas9 generated, SGPL1-knockout cell line (HeLa). Alterations to mitochondrial morphology suggest that SGPL1 deficiency impacts mitochondrial function. The 6 | P a g e complex interplay between sphingolipid biosynthetic defects, mitochondrial dynamics and steroidogenesis is key to understanding the phenotypic expression of disease. Variability in mitochondrial phenotype between both patient cell lines may be due to genetic heterogeneity or involvement of other components of the mitochondrial pathway independent of SGPL1. RNA-sequencing of a lentiviral mediated SGPL1 knockdown NCI-H295R (adrenocortical) cell line revealed transcriptome alterations consistent with downregulation of several key steroidogenic enzymes (STAR, CYP21A2, CYP11B1) and enrichment of genes and pathways implicated in cell proliferation, apoptosis and cholesterol biosynthesis. Gene mining highlighted an interesting candidate VAT1L (Vesicle amine transport 1 like), significantly downregulated and postulated to factor in pathogenesis of SPLIS. Generation of a CRISPR/Cas9 SGPL1 knockout H295R cell line validated the steroidogenic defect seen on RNA-seq with mRNA downregulation of STAR, CYP21A2 and CYP11B1 at baseline and reduced cortisol output on cyclic adenosine monophosphate (cAMP) stimulation. SGPL1 loss is postulated to affect steroid biosynthesis at multiple levels including abrogating steroidogenic factor-1 (SF-1) phosphorylation and processing of STAR as well as inhibition of the mitogen-activated protein kinase signaling pathway. Further work is needed to understand the molecular defects leading to multi-endocrine pathology in SPLIS and characterize the phenotypic heterogeneity associated with this disorder

A retrospective analysis of endocrine disease in sphingosine-1-phosphate lyase insufficiency: Case series and literature review

Sphingosine-1-phosphate lyase (SGPL1) insufficiency syndrome (SPLIS) is an autosomal recessive multi-system disorder, which mainly incorporates steroid-resistant nephrotic syndrome and primary adrenal insufficiency. Other variable endocrine manifestations are described. In this study, we aimed to comprehensively annotate the endocrinopathies associated with pathogenic SGPL1 variants and assess for genotype-phenotype correlations by retrospectively reviewing the reports of endocrine disease within our patient cohort and all published cases in the wider literature up to February 2022. Glucocorticoid insufficiency in early childhood is the most common endocrine manifestation affecting 64% of the 50 patients reported with SPLIS, and a third of these individuals have additional mineralocorticoid deficiency. While most individuals also have nephrotic syndrome, SGPL1 variants also account for isolated adrenal insufficiency at presentation. Primary gonadal insufficiency, manifesting with microphallus and cryptorchidism, is reported in less than one-third of affected boys, all with concomitant adrenal disease. Mild primary hypothyroidism affects approximately a third of patients. There is paucity of data on the impact of SGPL1 deficiency on growth, and pubertal development, limited by the early and high mortality rate (approximately 50%). There is no clear genotype-phenotype correlation overall in the syndrome, with variable disease penetrance within individual kindreds. However, with regards to endocrine phenotype, the most prevalent disease variant p.R222Q (affecting 22%) is most consistently associated with isolated glucocorticoid deficiency. To conclude, SPLIS is associated with significant multiple endocrine disorders. While endocrinopathy in the syndrome generally presents in infancy, late-onset disease also occurs. Screening for these is therefore warranted both at diagnosis and through follow-up

Isolated glucocorticoid deficiency: genetic causes and animal models

Hereditary adrenocorticotropin (ACTH) resistance syndromes encompass the genetically heterogeneous isolated or Familial Glucocorticoid Deficiency (FGD) and the distinct clinical entity known as Triple A syndrome. The molecular basis of adrenal resistance to ACTH includes defects in ligand binding, MC2R/MRAP receptor trafficking, cellular redox balance, cholesterol synthesis and sphingolipid metabolism. Biochemically, this manifests as ACTH excess in the setting of hypocortisolaemia. Triple A syndrome is an inherited condition involving a tetrad of adrenal insufficiency, achalasia, alacrima and neuropathy. FGD is an autosomal recessive condition characterized by the presence of isolated glucocorticoid deficiency, classically in the setting of preserved mineralocorticoid secretion. Primarily there are three established subtypes of the disease: FGD 1, FGD2 and FGD3 corresponding to mutations in the Melanocortin 2 receptor MC2R (25%), Melanocortin 2 receptor accessory protein MRAP (20%), and Steroidogenic acute regulatory protein STAR (5–10%) respectively. Together, mutations in these 3 genes account for approximately half of cases. Whole exome sequencing in patients negative for MC2R, MRAP and STAR mutations, identified mutations in minichromosome maintenance 4 MCM4, nicotinamide nucleotide transhydrogenase NNT, thioredoxin reductase 2 TXNRD2, cytochrome p450scc CYP11A1, and sphingosine 1-phosphate lyase SGPL1 accounting for a further 10% of FGD. These novel genes have linked replicative and oxidative stress and altered redox potential as a mechanism of adrenocortical damage. However, a genetic diagnosis is still unclear in about 40% of cases. We describe here an updated list of FGD genes and provide a description of relevant mouse models that, despite some being flawed, have been precious allies in the understanding of FGD pathobiology

Sphingosine-1-phosphate lyase mutations cause primary adrenal insufficiency and steroid-resistant nephrotic syndrome

Primary adrenal insufficiency is life threatening and can present alone or in combination with other comorbidities. Here, we have described a primary adrenal insufficiency syndrome and steroid-resistant nephrotic syndrome caused by loss-of-function mutations in sphingosine-1-phosphate lyase (SGPL1). SGPL1 executes the final decisive step of the sphingolipid breakdown pathway, mediating the irreversible cleavage of the lipid-signaling molecule sphingosine-1-phosphate (S1P). Mutations in other upstream components of the pathway lead to harmful accumulation of lysosomal sphingolipid species, which are associated with a series of conditions known as the sphingolipidoses. In this work, we have identified 4 different homozygous mutations, c.665G\u3eA (p.R222Q), c.1633_1635delTTC (p.F545del), c.261+1G\u3eA (p.S65Rfs*6), and c.7dupA (p.S3Kfs*11), in 5 families with the condition. In total, 8 patients were investigated, some of whom also manifested other features, including ichthyosis, primary hypothyroidism, neurological symptoms, and cryptorchidism. Sgpl1–/– mice recapitulated the main characteristics of the human disease with abnormal adrenal and renal morphology. Sgpl1–/– mice displayed disrupted adrenocortical zonation and defective expression of steroidogenic enzymes as well as renal histology in keeping with a glomerular phenotype. In summary, we have identified SGPL1 mutations in humans that perhaps represent a distinct multisystemic disorder of sphingolipid metabolism