Adrenal Insufficiency, Sex Reversal, and Angelman Syndrome due to Uniparental Disomy Unmasking a Mutation in CYP11A1

Primary Adrenal Insufficiency, Complete Sex Reversal, and Unique Clinical Phenotype in a Patient with Severe CYP11A1 (P450scc) Deficiency-Case Report and Literature Overview

BACKGROUND

Congenital adrenal hyperplasia (CAH) is a group of genetic disorders that lead to the dysfunction of the steroidogenesis pathway, resulting in steroid hormone deficiency of varied intensity. The cholesterol side-chain cleavage enzyme (P450scc), coded by the CYP11A1 gene, is vital to the first step in the biosynthesis of steroid hormones, which is the conversion of cholesterol to pregnenolone. Therefore, its deficiency causes a general steroid hormone shortage.

OBJECTIVE

We report a case of CAH caused by P450scc deficiency with complete 46, XY sex reversal, characteristic facial features (narrow middle section of the face, small ears with thick helix, fleshy upturned lobules), and dysmorphic macrocephaly along with shortened upper and lower extremities.

RESULTS

Our patient carries a compound heterozygotic pathogenic variant of the CYP11A1 gene, with two frameshift pathogenic variants NM_000781.3(CYP11A1):c.358del (p.Arg120Aspfs*18) in exon 2 and NM_000781.3(CYP11A1):c.835del (p.Ile279Tyrfs*10) in exon 5. To date, only around 50 cases with CYP11A1 pathogenic variants have been reported worldwide. We believe this is the first described case of a newborn with severe, classic P450scc deficiency in Poland.

CONCLUSIONS

CYP11A1 (P450scc) deficiency is a rare and complex disorder that leads to primary adrenal insufficiency and may present with 46, XY disorders of sex development (DSD), phenotypic variations, and associated endocrinological abnormalities. This case, along with others cited, highlights the diverse presentations of DSD in individuals with pathogenic CYP11A1 variants. Optimal management necessitates a multidisciplinary approach by a specialized DSD team. Gonadectomy is a key consideration to decrease the teratogenic risk associated with intra-abdominal gonadal tissue.

A CYP11A1 homozygous exonic variant inducing an alternative splicing, frameshift and truncation in a family with congenital adrenal hyperplasia

Background

Congenital adrenal hyperplasia (CAH) is a heterogeneous group of adrenal steroidogenesis disorders with variable degrees of glucocorticoid, mineralocorticoid and sex steroid deficiencies. CYP11A1 gene encodes the mitochondrial cholesterol side-chain cleavage enzyme (P450scc), which initiates the first reaction in steroidogenesis by converting cholesterol to pregnenolone. Variants in this gene are extremely rare but associated with severe forms of CAH due to its early and critical function in various steroid biosynthesis pathways. Here, we report a CYP11A1 exonic homozygous variant that, although exonic in location, affects splicing by creating an additional aberrant splicing site with frameshift and truncation of the gene.

Patients and methods

The proband is a 23-year old 46,XY patient raised as a girl. She was a product of normal pregnancy for first-degree relative parents. Soon after birth, she had vomiting, dehydration, hypotension, hyponatremia and hyperkalemia. She was started on glucocorticoids and mineralocorticoids with prompt recovery. Apart from a chronic need for these medications, her neonatal and childhood history was unremarkable. She sought medical advice at age 19 years for delayed puberty with primary amenorrhea and lack of breast development. On evaluation, she had normal external female genitalia, no breast development, undescended testes and absent uterus and ovaries. Her hormonal evaluation revealed very low estrogen, testosterone, cortisol, aldosterone, 17-hydroxyprogesterone, and androstenedione levels. ACTH, LH, FSH and renin were very high consistent with primary gonadal and adrenal failure. Her parents are healthy first-degree cousins. She has three sisters, all with 46,XX karyotype. One of them is clinically and biochemically normal while the other two sisters have normal female phenotype, normal uterus and ovaries, similar hormonal profile to the proband but different karyotype (46,XX) and absence of undescended testes. gDNA was used for whole exome sequencing (WES). Sanger sequencing was performed to confirm the detected variant and its segregation with the disease.

Results

WES identified a homozygous missense variant in CYP11A1 changing the second nucleotide (GCG > GTG) at position 189 in exon 3 and resulting in a change of Alanine to Valine (p.Ala189Val). This variant was confirmed by PCR and Sanger sequencing. It was found in a homozygous form in the proband and her two affected sisters and in a heterozygous form in the unaffected sister. In-silico analysis predicted this variant to create a new splicing site with frameshift and truncation of the gene transcript. This was confirmed by isolation of RNA, cDNA synthesis, gel electrophoresis and sequencing.

Conclusion

We describe a family with a very rare form of CAH due to a CYP11A1 variant leading to creation of a new splice site, frameshift and premature truncation of the protein.

Side-chain cleavage enzyme deficiency: Systematic review and case series

OBJECTIVE

P450 side-chain cleavage deficiency (SCCD) patients present with primary adrenal insufficiency (PAI) with or without undervirilized external genitalia. The distinction between classic and nonclassic steroidogenic acute regulatory protein deficiency has been described, whereas in SCCD is unclear. The data on gonadal function and its correlation with SCCD genotype has not been studied. We describe our experience and perform a systematic review of genetically proven SCCD patients to determine the distinct phenotypic and genotypic characteristics of 46,XY SCCD patients with typical male external genitalia (SCCD-TMG) and atypical (SCCD-AG) external genitalia.

DESIGN, PATIENTS AND MEASUREMENTS

Retrospective review of three genetically proven SCCD patients from our centre and per-patient data analysis from a systematic review of 52 probands was performed. SCCD-TMG (n = 19) was defined as external genitalia of Sinnecker score 1 with 46,XY  karyotype; the rest (Sinnecker 2-5) were classified as SCCD-AG (n = 15).

RESULTS

We report two new Indian cases of SCCD with three novel likely pathogenic variants and pubertal follow-up of a previously reported patient. In systematic review, age at diagnosis of PAI and elevated renin were not different between 46,XY  SCCD-TMG (n = 19) and SCCD-AG (n = 15), whereas spontaneous puberty (9/9 vs. 0/3, p = .0045), normal prepubertal (5/5 vs. 6/6, p = .002), pubertal gonadotropins (2/9 vs. 0/3, p = 1) and normal pubertal testosterone (9/11 vs. 0/3, p = .027) were more common in SCCD-TMG. Testicular adrenal rest tumours were exclusive to SCCD-TMG (n = 4). SCCD-TMG was associated with four particular genotypes [monoallelic p.Glu314Lys with another deleterious variant on the second allele (p.Glu314Lys/X-CHS: X-compound heterozygous state), biallelic p.Arg451Trp, p.Phe215Ser/p.Arg232Ter and monoallelic p.Val79Ile]. 46,XX SCCD  patients with p.Glu314Lys/X-CHS also had normal gonadotropins with spontaneous puberty.

CONCLUSION

SCCD-TMG is associated with four specific genotypes and distinct gonadal characteristics from SCCD-AG with overlapping features of PAI.

Circadian Rhythms and Sleep Are Dependent Upon Expression Levels of Key Ubiquitin Ligase Ube3a

Normal neurodevelopment requires precise expression of the key ubiquitin ligase gene Ube3a. Comparing newly generated mouse models for Ube3a downregulation (models of Angelman syndrome) vs. Ube3a upregulation (models for autism), we find reciprocal effects of Ube3a gene dosage on phenotypes associated with circadian rhythmicity, including the amount of locomotor activity. Consistent with results from neurons in general, we find that Ube3a is imprinted in neurons of the suprachiasmatic nuclei (SCN), the pacemaking circadian brain locus, despite other claims that SCN neurons were somehow exceptional to these imprinting rules. In addition, Ube3a-deficient mice lack the typical drop in wake late in the dark period and have blunted responses to sleep deprivation. Suppression of physical activity by light in Ube3a-deficient mice is not due to anxiety as measured by behavioral tests and stress hormones; quantification of stress hormones may provide a mechanistic link to sleep alteration and memory deficits caused by Ube3a deficiency, and serve as an easily measurable biomarker for evaluating potential therapeutic treatments for Angelman syndrome. We conclude that reduced Ube3a gene dosage affects not only neurodevelopment but also sleep patterns and circadian rhythms.

Blended phenotype of combination of HERC2 and AP3B2 deficiency and Angelman syndrome caused by paternal isodisomy of chromosome 15

Angelman syndrome is a neurodevelopmental disorder characterized by intellectual disability (ID), a distinctive gait pattern, abnormal behaviors, severe impairment in language development, and characteristic facial features. Most cases are caused by the absence of a maternal contribution to the imprinted region on chromosome 15q11-q13. Here, we present the first reported case of a 3-year-old boy with an atypical phenotype of Angelman syndrome due to uniparental isodisomy with two recessive homozygous pathogenic variants: in HERC2 and AP3B2. Known phenotypes related to HERC2 and AP3B2 include ID and early infantile epileptic encephalopathy, respectively. The patient had severe global developmental delay and profound ID and showed a happy demeanor, stereotypic laughter, and hand-flapping movements, but also irritability. Craniofacial dysmorphic features, including brachycephaly, strabismus, wide ala nasi, short philtrum, wide open mouth, and slight hypopigmentation were seen. Progressive microcephaly was noted. Magnetic resonance imaging of the brain showed delayed myelination and cerebral atrophy. Trio whole exome sequencing and CGH-SNP array analysis revealed paternal uniparental isodisomy of chromosome 15 and two coexisting recessive diseases resulting from homozygous HERC2 and AP3B2 pathogenic variants. The pathogenic variant in HERC2 was inherited from his heterozygous-carrier father, and the variant in AP3B2 was de novo. We suppose that these unusual features were the combination of the effect of three concomitant disorders.

Novel Mutations Segregating with Complete Androgen Insensitivity Syndrome and their Molecular Characteristics

We analyzed three cases of Complete Androgen Insensitivity Syndrome (CAIS) and report three hitherto undisclosed causes of the disease. RNA-Seq, Real-timePCR, Western immunoblotting, and immunohistochemistry were performed with the aim of characterizing the disease-causing variants. In case No.1, we have identified a novel androgen receptor (AR) mutation (c.840delT) within the first exon in the N-terminal transactivation domain. This thymine deletion resulted in a frameshift and thus introduced a premature stop codon at amino acid 282. In case No.2, we observed a nonsynonymous mutation in the ligand-binding domain (c.2491C>T). Case No.3 did not reveal AR mutation; however, we have found a heterozygous mutation in CYP11A1 gene, which has a role in steroid hormone biosynthesis. Comparative RNA-Seq analysis of CAIS and control revealed 4293 significantly deregulated genes. In patients with CAIS, we observed a significant increase in the expression levels of PLCXD3, TM4SF18, CFI, GPX8, and SFRP4, and a significant decrease in the expression of SPATA16, TSACC, TCP10L, and DPY19L2 genes (more than 10-fold, p < 0.05). Our findings will be helpful in molecular diagnostics of patients with CAIS, as well as the identified genes could be also potential biomarkers for the germ cells differentiation process.

Normal male external genitalia do not rule out CYP11A1 deficiency

Defects in the initial steps of steroidogenesis usually present with female external genitalia in both 46,XX and 46,XY. Hence, they are not often considered in the differential diagnosis of primary adrenal insufficiency children with normal male external genitalia. Here, we report a boy with normal male external genitalia who presented with hyperpigmentation since the age of 2 years but diagnosis was delayed till 11 years of age. Evaluation revealed low-serum cortisol with elevated adrenocorticotropic hormone and direct renin level confirming primary adrenal insufficiency. Clinical exome sequencing analysis revealed a homozygous c.1351C>T (p.R451W) mutation in exon 8 of the CYP11A1 gene which was confirmed on Sanger sequencing. Both parents were heterozygous for the variation. To conclude, we report the first case of CYP11A1 deficiency from India. The report reiterates the existence of non-classic CYP11A1 deficiency characterised by primary adrenal insufficiency and normal male external genitalia in 46,XY.