Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive genetic defects in cortisol synthesis and shows elevated ACTH concentrations, which in turn has downstream effects. The most ...common variant of CAH, 21-hydroxylase deficiency (21OHD), is the result of pathogenic variants in the
gene and is one of the most common monogenic disorders. However, the genetics of 21OHD is complex and challenging. The
gene is located in the RCCX copy number variation (CNV), a complex, multiallelic, and tandem CNV in the major histocompatibility complex (MHC) class III region on chromosome 6 (band 6p21.3). Here,
and its pseudogene
are located 30 kb apart and share a high nucleotide homology of approximately 98% and 96% in exons and introns, respectively. This high-sequence homology facilitates large structural rearrangements, copy number changes, and gene conversion through intergenic recombination. There is a good genotype-phenotype correlation in 21OHD, and genotyping can be performed to confirm the clinical diagnosis, predict long-term outcomes, and determine genetic counseling. Thus, genotyping in CAH is clinically relevant but the interpretations can be challenging for non-initiated clinicians. Here, there are some concrete examples of how molecular diagnosis can sometimes require the use of multiple molecular strategies.
RCCX haplotypes with two copies of the
CYP21A2
gene and one copy of the
CYP21A1P
pseudogene have been widely described in different populations. In most cases, the
CYP21A2-like
gene downstream of the
...TNXA
gene showed a wild-type sequence or the c.293-13A/C > G variant while the
CYP21A2
gene next to
TNXB
carried the p.(Gln319Ter) variant. Here is the discovery of a novel rare
CYP21A2
haplotypes detected in an Italian patient with Non Classical Congenital Adrenal Hyperplasia (NC-CAH). The molecular family study was performed clarifying the previously found phenotype-genotype discrepancy.
The first person-to-person transmission of the 2019-novel coronavirus in Italy on 21 February 2020 led to an infection chain that represents one of the largest known COVID-19 outbreaks outside Asia. ...Hospitals have been forced to reorganized their units in response to prepare for an unforeseen healthcare emergency. In this context, our laboratory (
Molecular and Genomic Diagnostics Unit
,
Fondazione Policlinico Universitario Agostino Gemelli IRCCS
) re-modulated its priorities by temporarily interrupting most of the molecular tests guaranteeing only those considered “
urgent”
and not postponable. In particular, this paper details changes regarding the execution of germline
BRCA
(
gBRCA
) testing in our laboratory. A substantial reduction in
gBRCA
testing (about 60%) compared to the first 2 months of the current year was registered, but the requests have not been reset. The requesting physicians were mainly gynaecologists and oncologists. These evidences further emphasize the new
era
of
gBRCA
testing in the management of cancer patients and confirms definitively the integration of
gBRCA
testing/Next Generation Sequencing (NGS) into clinical oncology. Finally, a re-organization of
gBRCA
testing in our Unit, mainly related to delayed and reduced arrival of tests was necessary, ensuring, however, a high-quality standard and reliability, mandatory for
gBRCA
testing in a clinical setting.
Substantial research has been performed during the last decades on the clinical and genetic variability of congenital adrenal hyperplasia (CAH) and its most common form, 21-hydroxylase deficiency ...(21OHD). CAH is one of the most prevalent autosomal recessive diseases in humans, and it can be divided into classic-further subdivided into salt wasting (SW) and simple virilizing (SV)-and non-classic (NC) forms. Pathogenic variants of
gene, encoding the 21-hydroxylase enzyme, have been reported with variable prevalence in different populations. NM_000500.9:c.293-13C/A>G (In2G) variant represents the most common
gene changes related to the classic 21OHD form. However, the phenotype of In2G carriers is variable depending on the variant homozygous/heterozygous status and combination with other
pathogenic variants. In addition, identical genotypes, harboring the homozygous In2G variant, can present with variable phenotypes including the SW and SV or rarely NC form of the disease. Here, we analyze and present the clinical aspects, genotype/phenotype correlations, and other characteristics related to the
In2G variant.
Copy Number Variations (CNVs) account for a large proportion of human genome and are a primary contributor to human phenotypic variation, in addition to being the molecular basis of a wide spectrum ...of disease. Multiallelic CNVs represent a considerable fraction of large CNVs and are strictly related to segmental duplications according to their prevalent duplicate alleles. RCCX CNV is a complex, multiallelic and tandem CNV located in the major histocompatibility complex (MHC) class III region. RCCX structure is typically defined by the copy number of a DNA segment containing a series of genes - the serine/threonine kinase 19 (
), the complement 4 (
), the steroid 21-hydroxylase (
), and the tenascin-X (
) - lie close to each other. In the Caucasian population, the most common RCCX haplotype (69%) consists of two segments containing the genes
, with a telomere-to-centromere orientation. Nonallelic homologous recombination (NAHR) plays a key role into the RCCX genetic diversity: unequal crossover facilitates large structural rearrangements and copy number changes, whereas gene conversion mediates relatively short sequence transfers. The results of these events increased the RCCX genetic diversity and are responsible of specific human diseases. This review provides an overview on RCCX complexity pointing out the molecular bases of Congenital Adrenal Hyperplasia (CAH) due to CYP21A2 deficiency, CAH-X Syndrome and disorders related to CNV of complement component C4.
Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive genetic defects in cortisol synthesis and shows elevated ACTH concentrations, which in turn has downstream effects. The most ...common variant of CAH, 21-hydroxylase deficiency (21OHD), is the result of pathogenic variants in the CYP21A2 gene and is one of the most common monogenic disorders. However, the genetics of 21OHD is complex and challenging. The CYP21A2 gene is located in the RCCX copy number variation (CNV), a complex, multiallelic, and tandem CNV in the major histocompatibility complex (MHC) class III region on chromosome 6 (band 6p21.3). Here, CYP21A2 and its pseudogene CYP21A1P are located 30 kb apart and share a high nucleotide homology of approximately 98% and 96% in exons and introns, respectively. This high-sequence homology facilitates large structural rearrangements, copy number changes, and gene conversion through intergenic recombination. There is a good genotype–phenotype correlation in 21OHD, and genotyping can be performed to confirm the clinical diagnosis, predict long-term outcomes, and determine genetic counseling. Thus, genotyping in CAH is clinically relevant but the interpretations can be challenging for non-initiated clinicians. Here, there are some concrete examples of how molecular diagnosis can sometimes require the use of multiple molecular strategies.
Iodothyronine deiodinases are selenoproteins that regulate thyroid hormone metabolism. Of the three types of deiodinases, type 2 is the major regulator of intracellular triiodothyronine concentration ...in both the hypothalamus and pituitary, and therefore the major regulator of thyrotropin secretion. A defect in iodothyronine deiodinase activity can lead to a reduced sensitivity to thyroid hormones action and the most recent literature includes these defects in the so-called "syndromes of reduced sensitivity to thyroid hormones". To date, the pathogenic variants of the selenocysteine insertion sequence-binding protein 2 (
) gene are the first and only inherited disorder of iodothyronine metabolism described. Moreover, there is a growing interest in understanding the possible role of polymorphisms of
and
genes in some pathological conditions and in determining the requirement of levothyroxine replacement and the role of combined levothyroxine-liothyronine therapy in carrying subjects affected by hypothyroidism and who need replacement therapy. Results on this topic are still conflicting and more studies are needed to assess the efficacy of combined levothyroxine-liothyronine replacement therapy in this subset of patients.
We describe the complex case of a 44-year-old man with polycystic kidney disease, mild cognitive impairment, and tremors in the upper limbs. Brain MRI showed lesions compatible with leukodystrophy. ...The diagnostic process, which included clinical exome sequencing (CES) and chromosomal microarray analysis (CMA), revealed a triple diagnosis: autosomal dominant polycystic kidney disease (ADPKD) due to a pathogenic variant, c.2152C>T-p.(Gln718Ter), in the
gene; late-onset phenylketonuria due to the presence of two missense variants, c.842C>T-p.(Pro281Leu) and c.143T>C-p.(Leu48Ser) in the
gene; and a 915 Kb duplication on chromosome 15. Few patients with multiple concurrent genetic diagnoses are reported in the literature; in this ADPKD patient, genome-wide analysis allowed for the diagnosis of adult-onset phenylketonuria (which would have otherwise gone unnoticed) and a 15q11.2 duplication responsible for cognitive and behavioral impairment with incomplete penetrance. This case underlines the importance of clinical genetics for interpreting complex results obtained by genome-wide techniques, and for diagnosing concurrent late-onset monogenic conditions.
The aim of this report is to describe results of
and
Next Generation Sequencing Analysis (NGS) analysis in 132 selected Italian patients with breast/ovarian cancer. A NGS pipeline with a reliable ...Copy Number Variation (CNV) prediction algorithm was applied. In addition, VarSome and Priors V2.0 Software were employed for in silico analysis of novel missense variants. A total of 37
and
pathogenic variants were found in 34 unrelated subjects with a frequency of positive patients of 25.7% (34/132). Twenty-four deleterious variants were detected in
(representing the 64.9% of all identified pathogenic defects) and thirteen (35.1% of all identified pathogenic variants) in
gene. The percentage of patients carrying a variant of unknown significance (VUS) was 7.5% (10/132). In addition, seven novel variants (five in
and two in
gene), never previously reported, were identified. Our approach represents a robust and easy-to-use method for full
screening. However, a consistent number of our high-risk families still remained without a satisfying answer. Necessarily, further collective efforts must be directed to a definitive classification of VUSs. The future auspice is that the use of multi-gene panel and more advanced screenings, such as whole exome sequencing and/or RNA seq, in routine diagnostics increases the detection rate.
Deficiency of 11β-hydroxylase (11β-OHD) is the second most common cause of congenital adrenal hyperplasia (CAH), accounting for 0.2-8% of all cases. The disease is transmitted as an autosomal ...recessive trait and the underlying genetic causes of 11β-OHD are primarily small pathogenic variants affecting the CYP11B1 gene coding the 11β-hydroxylase enzyme. However, special events complicate the molecular diagnosis of 11β-OHD such as an unequal crossing over between the CYP11B2 (coding aldosterone synthase enzyme) and CYP11B1 genes. The resulting allele contains a hybrid gene, with a CYP11B2 5'-end and a CYP11B1 3'-end, where the CYP11B1 gene is under the control of the CYP11B2 promoter and thus not responding to the adrenocorticotropin (ACTH) but to angiotensin II and K
. This leads a reduction of cortisol production in 11β-OHD. In particular, CYP11B2/CYP11B1 chimeric genes can be distinguished into two groups depending on the breakpoint site: chimeras with breakpoint after the exon 5 of CYP11B2 preserve the aldosterone synthase activity, the others with breakpoint before exon 5 lose this function. In the last case, a more severe phenotype is expected. The aim of this review was to explore the setting of CYP11B2/CYP11B1 chimeras in 11β-OHD, performing a careful review of clinical literature cases.
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