Does the esv3587290 Copy Number Variation in the VANGL1 Gene Differ as a Genetic Factor for Developing Nephritis in Mexican Childhood-Onset Systemic Lupus Erythematosus Patients?

A ~3-kb deletion-type DNA copy number variation (CNV, esv3587290) located at intron 7 of the VANGL1 gene (1p13.1, MIM*610132) has been proposed as a genetic factor in lupus nephritis (LN) development in adult systemic lupus erythematosus (SLE) patients across European-descent populations, but its replication in other ethnicities has been inconsistent and its association with LN in childhood-onset SLE (cSLE) remains unknown. Here, we performed an exploratory association study in a sample of 66 unrelated cSLE Mexican patients (11 males, 55 females; ages 7.8 to 18.6 years). Two stratified groups were compared: cSLE patients with (N = 39) or without (N = 27) LN, as diagnosed by renal biopsy (N = 17), proteinuria (N = 33), urinary protein-creatinine ratio > 0.2 (N = 34), and erythrocyturia and/or granular casts in urinary sediment (N = 16). For esv3587290 CNV genotyping, we performed an end-point PCR assay with breakpoint confirmation using Sanger sequencing. We also determined the allelic frequencies of the esv3587290 CNV in 181 deidentified ethnically matched individuals (reference group). The obtained genotypes were tested for Hardy-Weinberg equilibrium using the χ2 test. Associations between LN and esv3587290 CNV were tested by calculating the odds ratio (OR) and using Pearson's χ2 tests, with a 95% confidence interval and p ≤ 0.05. The esv3587290 CNV allele (OR 0.108, 95% CI 0.034-0.33, p = 0.0003) and the heterozygous genotype (OR 0.04, 95% CI 0.119-0.9811, p = 0.002) showed a significant protective effect against LN development. Finally, we characterized the precise breakpoint of the esv3587290 CNV to be NG_016548.1(NM_138959.3):c.1314+1339_1315-897del in our population. This report supports the notion that a broad genetic heterogeneity underlies the susceptibility for developing LN.

In Silico Structural Protein Evaluation of the Phenylalanine Hydroxylase p.(Tyr77His) Variant Associated with Benign Hyperphenylalaninemia as Identified through Mexican Newborn Screening.

Hyperphenylalaninemia (HPA), which includes phenylketonuria (PKU), is a genetic autosomal recessive disorder arising from a deficiency in the enzyme named phenylalanine hydroxylase (PAH). Affected patients can experience severe and irreversible neurological impairments when phenylalanine (Phe) blood concentration exceeds 360 µmol/L (6 mg/dL). Here, we describe a female HPA patient who was born in Mexico to Cuban non-consanguineous parents and identified by newborn screening, and who bears the previously unreported PAH NM_000277.3(PAH):c.[229T>C];[1222C>T] or p.[Tyr77His];[Arg408Trp] genotype. At diagnosis, the patient showed a Phe blood level of 321 µmol/L (5.3 mg/dL), indicative of mild HPA. Neither of the PAH variants found in this patient had been previously reported in the mutational PAH spectrum of the Mexican population. The c.229T>C or p.(Tyr77His) PAH variant was previously related to mild HPA in the Swedish population. Our in silico structural analysis and molecular docking showed that mutated His 77 residue is located in the allosteric site of PAH at the interface of the two monomers. The PDBsum in silico tool predicted that this variant would cause minimal structural disturbance of the protein interface in the presence of Phe at the allosteric site. Docking studies revealed that these structural changes might be attenuated by the allosteric effect of Phe. Given the classic PKU phenotype conditioned by the "Celtic" or c.[1222C>T] or p.(Arg408Trp) PAH variant, which is the second variant in this patient, we propose that p.(Tyr77His) has a hypomorphic feature that could explain her mild HPA phenotype. Our results show the importance of following up on cases detected by NBS and the value of genetic studies and in silico tools that aid in the establishment of correct therapeutic strategies.

Unusual Trisomy X Phenotype Associated with a Concurrent Heterozygous 16p11.2 Deletion: Importance of an Integral Approach for Proper Diagnosis.

Trisomy X is the most frequent sex chromosome anomaly in women, but it is often underdiagnosed postnatally because most patients do not show any clinical manifestation. It is estimated that only 10% of patients with trisomy X are diagnosed by clinical findings. Thus, it has been proposed that the clinical spectrum is not yet fully delimited, and additional uncommon or atypical clinical manifestations could be related to this entity. The present report describes a female carrying trisomy X but presenting atypical manifestations, including severe intellectual disability, short stature, thymus hypoplasia, and congenital hypothyroidism (CH). These clinical findings were initially attributed to trisomy X. However, chromosome microarray analysis (CMA) subsequently revealed that the patient also bears a heterozygous 304-kb deletion at 16p11.2. This pathogenic copy-number variant (CNV) encompasses 13 genes, including TUFM. Some authors recommend that when a phenotype differs from that described for an identified microdeletion, the presence of pathogenic variants in the non-deleted allele should be considered to assess for an autosomal recessive disorder; thus, we used a panel of 697 genes to rule out a pathogenic variant in the non-deleted TUFM allele. We discuss the possible phenotypic modifications that might be related to an additional CNV in individuals with sex chromosome aneuploidy (SCA), as seen in our patient. The presence of karyotype-demonstrated trisomy X and CMA-identified 16p11.2 deletion highlights the importance of always correlating a patient's clinical phenotype with the results of genetic studies. When the phenotype includes unusual manifestations and/or exhibits discrepancies with that described in the literature, as exemplified by our patient, a more extensive analysis should be undertaken to enable a correct diagnosis that will support proper management, genetic counseling, and medical follow-up.

Uncommon Large and Bilateral Fibrous Cephalic Plaques in a Patient with TSC2-Related Tuberous Sclerosis Complex.

Tuberous sclerosis complex (TSC) is a genetic disorder, frequently characterized by early dermatological manifestations. The recognition and adequate description of these dermatological manifestations are of utmost importance for early diagnosis, allowing for the implementation of therapeutic and preventive measures. Fibrous cephalic plaques (FCPs) are considered a major diagnostic criterion for TSC, as FCPs are the most specific skin lesions of TSC. The localization, consistency, color, and size of FCPs vary widely, which can cause diagnostic delay, especially in patients with atypical presentations. The present report describes a female TSC patient with a confirmed heterozygous pathogenic genotype, NG_005895.1 (TSC2_v001): c.2640-1G>T, who presented with uncommon large and bilateral FCPs causing bilateral ptosis and marked with hyperostosis of the diploe that generated an asymmetry of the brain parenchyma. Differential diagnoses considered initially in this patient due to the atypical FCPs are described.

Clinical, pathological, and molecular correlation of folliculocystic and collagen hamartoma: A new potential diagnostic criterion for tuberous sclerosis complex?

Folliculocystic and collagen hamartoma (FCCH) is a rare entity with only 18 reported cases worldwide. Of them, most are found in patients diagnosed with tuberous sclerosis complex (TSC). FCCH has distinctive histopathologic features, including collagen deposition in the dermis, perifollicular fibrosis, and comedones with keratin-containing cysts lined by infundibular epithelium. We report three patients with a definitive TSC clinical diagnosis in whom clinical, histopathologic, and molecular features were studied to establish if there exists a genotype-phenotype correlation. The molecular results showed different heterozygous pathogenic variants (PV) in TSC2 in each patient: NM_000548.4:c.5024C>T, NG_005895.1:c.1599+1G>T, and NM_000548.4:c.2297_2298dup, to our knowledge; the latter PV has not been reported in public databases. The same PVs were identified as heterozygous in the tumor tissue samples, none of which yielded evidence of a TSC2 second hit. Because all FCCH patients with available molecular diagnosis carry a pathogenic genotype in TSC1 or TSC2, we suggest that FCCH should be considered as a new and uncommon diagnostic manifestation in the TSC consensus international diagnostic criteria. The early recognition of FCCH by clinicians could prompt the identification of new TSC cases. Interestingly, our molecular findings suggest that one of the patients described herein is a probable case of somatic mosaicism.

The Enigmatic Etiology of Oculo-Auriculo-Vertebral Spectrum (OAVS): An Exploratory Gene Variant Interaction Approach in Candidate Genes.

The clinical diagnosis of oculo-auriculo-vertebral spectrum (OAVS) is established when microtia is present in association with hemifacial hypoplasia (HH) and/or ocular, vertebral, and/or renal malformations. Genetic and non-genetic factors have been associated with microtia/OAVS. Although the etiology remains unknown in most patients, some cases may have an autosomal dominant, autosomal recessive, or multifactorial inheritance. Among the possible genetic factors, gene−gene interactions may play important roles in the etiology of complex diseases, but the literature lacks related reports in OAVS patients. Therefore, we performed a gene−variant interaction analysis within five microtia/OAVS candidate genes (HOXA2, TCOF1, SALL1, EYA1 and TBX1) in 49 unrelated OAVS Mexican patients (25 familial and 24 sporadic cases). A statistically significant intergenic interaction (p-value < 0.001) was identified between variants p.(Pro1099Arg) TCOF1 (rs1136103) and p.(Leu858=) SALL1 (rs1965024). This intergenic interaction may suggest that the products of these genes could participate in pathways related to craniofacial alterations, such as the retinoic acid (RA) pathway. The absence of clearly pathogenic variants in any of the analyzed genes does not support a monogenic etiology for microtia/OAVS involving these genes in our patients. Our findings could suggest that in addition to high-throughput genomic approaches, future gene−gene interaction analyses could contribute to improving our understanding of the etiology of microtia/OAVS.

Unusual Clinical Manifestations in a Mexican Patient with Sanfilippo B Syndrome.

We present an unusual Mexican patient affected with mucopolysaccharidosis type IIIB (MPS IIIB; also called Sanfilippo B syndrome, MIM #252920) bearing clinical features that have not previously been described for MPS IIIB (growth arrest, hypogonadotropic hypogonadism, and congenital heart disease). Chromosomal microarray analysis was useful in identifying runs of homozygosity at 17q11.1-q21.33 and supporting the diagnosis of an underlying autosomal recessive condition. Sanger sequencing of NAGLU (17q21.2, MIM*609701) allowed us to identify a pathogenic homozygous p.(Arg234Cys) genotype. This NAGLU allele could be related to that previously described in an Iberian MPS IIIB founder haplotype; results from the polymorphic marker D17S800 and rs2071046 led us to hypothesize that it may have been introduced to Mexico through the Spanish settlement. The analysis of a clinical exome sequencing ruled out other monogenic etiologies for the previously undescribed clinical MPS IIIB manifestations. Our findings contribute to further delineating the MPS IIIB phenotype and suggest possible phenotype-genotype correlations.

Proposed clinical approach and imaging studies in families with oculo-auriculo-vertebral spectrum to assess variable expressivity.

A diagnosis of oculo-auriculo-vertebral spectrum (OAVS) is established when microtia is present in association with hemifacial hypoplasia (HH) and/or ocular, vertebral, and/or renal malformations. There is no consensus on which imaging studies should be used to rule out variable expressivity and distinguish "sporadic" from "familial" patients. This observational and descriptive study was performed in a Mexican population of 51 patients (32 males, 19 females, 0-18 years old) with microtia/OAVS, and their available parents. A clinical history, genealogy, and physical examination were obtained from all included patients, as were a computed tomography (CT) scan of the ear, audiological evaluation, orthopantomography, complete spine radiography, and renal ultrasound. The same approach was completed in their available parents (51 mothers and 40 fathers), excluding the CT scan and audiological evaluation. By genealogy, 53% of patients were classified as "sporadic"; of the "familial" patients, at least 79.1% had suggestion of a multifactorial inheritance. In the available parents, orthopantomography, complete spine X-ray, and renal ultrasound identified the following OAVS-related manifestations: HH (16.2%, n = 14/86), vertebral alterations (10.9%, n = 10/91), and renal anomalies (2.2%, n = 2/90). Our evaluation of the parents allowed three patients to be reclassified from "sporadic" to "familial" (5.8%, n = 3/51). Our proposed clinical and imaging approach allowed the identification of variable expressivity that more clearly distinguished between "sporadic" and "familial" OAVS patients, which is of utmost importance in providing proper genetic counseling to these families.

An Updated PAH Mutational Spectrum of Phenylketonuria in Mexican Patients Attending a Single Center: Biochemical, Clinical-Genotyping Correlations.

Establishing the genotypes of patients with hyperphenylalaninemia (HPA)/phenylketonuria (PKU, MIM#261600) has been considered a cornerstone for rational medical management. However, knowledge of the phenylalanine hydroxylase gene (PAH) mutational spectrum in Latin American populations is still limited. Herein, we aim to update the mutational PAH spectrum in the largest cohort of HPA/PKU Mexican patients (N = 124) reported to date. The biallelic PAH genotype was investigated by Sanger automated sequencing, and genotypes were correlated with documented biochemical phenotypes and theoretical tetrahydrobiopterin (BH4) responsiveness. Patients were biochemically classified as having classic PKU (50%, 62/124), mild PKU (20.2%, 25/124) and mild HPA (29.8%, 37/124). Furthermore, 78.2% of the included patients (97/124) were identified by newborn screening. A total of 60 different pathogenic variants were identified, including three novel ones (c. 23del, c. 625_626insC and c. 1315 + 5_1315 + 6insGTGTAACAG), the main categories being missense changes (58%, 35/60) and those affecting the catalytic domain (56.6%, 34/60), and c. 60 + 5G > T was the most frequent variant (14.5%, 36/248) mainly restricted (69.2%) to patients from the central and western parts of Mexico. These 60 types of variants constituted 100 different biallelic PAH genotypes, with the predominance of compound-heterozygous ones (96/124, 77%). The expected BH4 responsiveness based on the PAH genotype was estimated in 52% of patients (65/124), mainly due to the p. (Val388Met) (rs62516101) allele. Instead, our study identified 27 null variants with an allelic phenotype value of zero, with a predominance of c. 60 + 5G > T, which predicts the absence of BH4 responsiveness. An identical genotype reported in BIOPKUdb was found in 92/124 (74%) of our patients, leading to a genotype-phenotype concordance in 80/92 (86.9%) of them. The high number of variants found confirms the heterogeneous and complex mutational landscape of HPA/PKU in Mexico.

Whole-genome amplification/preimplantation genetic testing for propionic acidemia of successful pregnancy in an obligate carrier Mexican couple: A case report.

BACKGROUND: Identifying a potential single monogenetic disorder in healthy couples is costly due to the Assisted Reproduction facilities' current methodology for screening, which focuses on the detecting multiple genetic disorders at once. Here, we report the successful application of a low-cost and fast preimplantation genetic testing for monogenic/single gene defects (PGT-M) approach for detecting propionic acidemia (PA) in embryos obtained from a confirmed heterozygous propionyl-CoA carboxylase alpha subunit (PCCA) couple. CASE SUMMARY: A fertile 32-years old Mexican couple with denied consanguinity sought antenatal genetic counseling. They were suspected obligate PA carriers due to a previous deceased PA male newborn with an unknown PCCA/propionyl-CoA carboxylase beta subunit (PCCB) genotype. Next-Generation Sequencing revealed a heterozygous genotype for a pathogenic PCCA variant (c.2041-1G>T, ClinVar:RCV000802701.1; dbSNP:rs1367867218) in both parents. The couple requested in vitro fertilization (IVF) and PGT-M for PA. From IVF, 12 oocytes were collected and fertilized, of which two resulted in high-quality embryos. Trophectoderm biopsies and Whole Genome Amplification by a fragmentation/amplification-based method were performed and revealed that the two embryos were euploid. End-point polymerase chain reaction and further Sanger sequencing of the exon-intron borders revealed a wild-type PCCA male embryo and a heterozygous c.2041-1G>T female embryo. Both embryos were transferred, resulting in a clinical pregnancy and the delivery of a healthy male newborn (38 wk, weight: 4080 g, length: 49 cm, APGAR 9/9). The absence of PA was confirmed by expanded newborn screening. CONCLUSION: We show that using PGT-M with Whole Genome Amplification templates, coupled with IVF, can reduce the transmission of a pathogenic variant of the PCCA gene.

Further Evidence That Defects in Main Thyroid Dysgenesis-Related Genes Are an Uncommon Etiology for Primary Congenital Hypothyroidism in Mexican Patients: Report of Rare Variants in FOXE1, NKX2-5 and TSHR.

Mexico shows a high birth prevalence of congenital hypothyroidism (CH) due to thyroid dysgenesis (TD). PAX8 defects underlie only 1% of these cases and NKX2-1 does not seem to be involved. Here, we analyzed other TD-related genes in 128 non-related Mexican patients (females 77.3%; 6 months to 16.6 years) with non-syndromic CH-TD diagnosis established by clinical evaluation, thyroid hormone serum profiling, and scintigraphy (74%) or ultrasonography (26%). We performed Sanger sequencing of FOXE1, NKX2-5, and TSHR and evaluated copy number variations (CNVs) in TSHR, FOXE1, PAX8, and NKX2-1 by multiplex ligation-dependent probe amplification. Odds ratios for TD risk were explored for FOXE1 polyalanine stretches [polyAla-rs71369530] in cases and controls (N = 116). Five rare missense changes cataloged as benign (NKX2-5:p.(Ala119Ser)-rs137852684), of unknown significance (FOXE1:p.(Ala335Gly)-rs543372757; TSHR:p.(Asp118Asn)-rs1414102266), and likely pathogenic (FOXE1:p.(Gly124Arg)-rs774035532; TSHR:p.(Trp422Arg)-rs746029360) accounted for 1.5% (N = 2/128) of clinically relevant genotypes (supported in part by protein modeling) in CH-TD. No CNVs were identified, nor did polyAla > 14 alanines in FOXE1 significantly protect against TD. The present and previously published data collectively show that small clinically relevant germline variants in PAX8, FOXE1, and TSHR are found in only a very small proportion (2.5%) of isolated CH-TD Mexican patients.

Genetic spectrum and clinical early natural history of glucose-6-phosphate dehydrogenase deficiency in Mexican children detected through newborn screening.

BACKGROUND: Glucose-6-phosphate dehydrogenase deficiency (G6PDd) newborn screening is still a matter of debate due to its highly heterogeneous birth prevalence and clinical expression, as well as, the lack of enough knowledge on its natural history. Herein, we describe the early natural clinical course and the underlying GDPD genotypes in infants with G6PDd detected by newborn screening and later studied in a single follow-up center. G6PDd newborns were categorized into three groups: group 1: hospitalized with or without neonatal jaundice (NNJ); group 2: non-hospitalized with NNJ; and group 3: asymptomatic. Frequencies of homozygous UGT1A1*28 (rs34983651) genotypes among G6PDd patients with or without NNJ were also explored. RESULTS: A total of 81 newborns (80 males, one female) were included. Most individuals (46.9%) had NNJ without other symptoms, followed by asymptomatic (42.0%) and hospitalized (11.1%) patients, although the hospitalization of only 3 of these patients was related to G6PDd, including NNJ or acute hemolytic anemia (AHA). Nine different G6PDd genotypes were found; the G6PD A-202A/376G genotype was the most frequent (60.5%), followed by the G6PD A-376G/968C (22.2%) and the Union-Maewo (rs398123546, 7.4%) genotypes. These genotypes produce a wide range of clinical and biochemical phenotypes with significant overlapping residual enzymatic activity values among class I, II or III variants. Some G6PD A-202A/376G individuals had enzymatic values that were close to the cutoff value (5.3 U/g Hb, 4.6 and 4.8 U/g Hb in the groups with and without NNJ, respectively), while others showed extremely low enzymatic values (1.1 U/g Hb and 1.4 U/g Hb in the groups with and without NNJ, respectively). Homozygosity for UGT1A1*28 among G6PDd patients with (11.9%, N = 5/42) or without (10.3%, N = 4/39) NNJ did not shown significant statistical difference (p = 0.611). CONCLUSION: Wide variability in residual enzymatic activity was noted in G6PDd individuals with the same G6PD genotype. This feature, along with a documented heterogeneous mutational spectrum, makes it difficult to categorize G6PD variants according to current WHO classification and precludes the prediction of complications such as AHA, which can occur even with > 10% of residual enzymatic activity and/or be associated with the common and mild G6PD A-376G/968C and G6PD A-202A/376G haplotypes.

Predominance of Dystrophinopathy Genotypes in Mexican Male Patients Presenting as Muscular Dystrophy with A Normal Multiplex Polymerase Chain Reaction DMD Gene Result: A Study Including Targeted Next-Generation Sequencing.

The complete mutational spectrum of dystrophinopathies and limb-girdle muscular dystrophy (LGMD) remains unknown in Mexican population. Seventy-two unrelated Mexican male patients (73% of pediatric age) with clinical suspicion of muscular dystrophy and no evidence of DMD gene deletion on multiplex polymerase chain reaction (mPCR) analysis were analyzed by multiplex ligation-dependent probe amplification (MLPA). Those with a normal result were subjected to Sanger sequencing or to next-generation sequencing for DMD plus 10 selected LGMD-related genes. We achieved a diagnostic genotype in 80.5% (n = 58/72) of patients with predominance of dystrophinopathy-linked genotypes (68%, n = 49/72), followed by autosomal recessive LGMD-related genotypes (types 2A-R1, 2C-R5, 2E-R4, 2D-R3 and 2I-R9; 12.5%, n = 9/72). MLPA showed 4.2% of false-negatives for DMD deletions assessed by mPCR. Among the small DMD variants, 96.5% (n = 28/29) corresponded to null-alleles, most of which (72%) were inherited through a carrier mother. The FKRP p.[Leu276Ile]; [Asn463Asp] genotype is reported for the first time in Mexican patients as being associated with dilated cardiomyopathy. Absence of dysferlinopathies could be related to the small sample size and/or the predominantly pediatric age of patients. The employed strategy seems to be an affordable diagnosis approach for Mexican muscular dystrophy male patients and their families.

Mutational spectrum of Mexican patients with tyrosinemia type 1: In silico modeling and predicted pathogenic effect of a novel missense FAH variant.

BACKGROUND: Tyrosinemia type 1 (HT1, MIM#276700) is caused by a deficiency in fumarylacetoacetate hydrolase (FAH) and it is associated with severe liver and renal disfunction. At present, the mutational FAH (15q25.1, MIM*613871) spectrum underlying HT1 in the Mexican population is unknown. The objective of this study was to determine the FAH genotypes in eight nonrelated Mexican patients with HT1, who were diagnosed clinically. METHODS: Sequencing of FAH and their exon-intron boundaries and in silico protein modeling based on the crystallographic structure of mouse FAH. RESULTS: We identified pathogenic variants in 15/16 studied alleles (93.8%). Nine different variants were found. The most commonly detected HT1-causing allele was NM_000137.2(FAH):c.3G > A or p.(?) [rs766882348] (25%, n = 4/16). We also identified a novel missense variant NM_000137.2(FAH):c.36C > A or p.(Phe12Leu) in a homozygous patient with an early and fatal acute form. The latter was classified as a likely pathogenic variant and in silico protein modeling showed that Phe-12 residue substitution for Leu, produces a repulsion in all possible Leu rotamers, which in turn would lead to a destabilization of the protein structure and possible loss-of-function. CONCLUSION: HT1 patients had a heterogeneous mutational and clinical spectrum and no genotype-phenotype correlation could be established.

Skewed X-inactivation in a Female Carrier with X-linked Chronic Granulomatous Disease.

Chronic granulomatous disease (CGD) is a primary immunodeficiency caused by defective phagocytic NADPH oxidase, causing a complete lack or significant decrease in the production of microbicidal reactive oxygen metabolites. It mainly affects male children; however, there are scarce reports of adult females diagnosed with X-linked-CGD attributed to an extremely skewed X-chromosome inactivation. This condition is characterized by severe and recurrent infections that usually develop after childhood. In clinical practice, physicians who usually confront these patients should suspect this entity and differentiate it from a secondary immunodeficiency. Here, we report a 38-year-old Mexican female with juvenile-onset X linked-CGD, caused by a de novo mutation and extremely skewed X-inactivation, whose clinical features were similar to those in patients with classic X-linked-CDG.

Gene Variants in NKX2-1 Do Not Represent a Major Etiological Factor of Primary Congenital Hypothyroidism in Mexican Population.

Congenital hypothyroidism (CH), attributable to thyroid dysgenesis (TD), has an unusually high prevalence in Mexican population but the causes are unknown. NKX2-1 , as a candidate gene, was subjected to automated Sanger sequencing in 122 unrelated Mexican patients with CH/TD. Although this study includes the largest number of TD-related CH patients in whom NKX2-1 has been analyzed, no pathogenic variants were detected; only three benign polymorphic changes were identified. These results suggest that NKX2-1 is not a major contributor to the etiology of CH or its high prevalence in Mexicans. Our work identifies misannotations of NKX2-1 variants in three previous published reports.

Molecular characterization of Axenfeld-Rieger spectrum and other anterior segment dysgeneses in a sample of Mexican patients.

BACKGROUND: Anterior segment dysgenesis (ASD) and Axenfeld-Rieger spectrum (ARS) are mainly due to PITX2 and FOXC1 defects, but it is difficult in some patients to differentiate among PITX2-, FOXC1-, PAX6- and CYP1B1-related disorders. Here, we set out to characterize the pathogenic variants (PV) in PITX2, FOXC1, CYP1B1 and PAX6 in nine unrelated Mexican ARS/ASD patients and in their available affected/unaffected relatives. MATERIALS AND METHODS: Automated Sanger sequencing of PITX2, FOXC1, PAX6 and CYP1B1 was performed; those patients without a PV were subsequently analyzed by Multiplex Ligation-dependent Probe Amplification (MLPA) for PITX2, FOXC1 and PAX6. Missense variants were evaluated with the MutPred, Provean, PMUT, SIFT, PolyPhen-2, CUPSAT and HOPE programs. RESULTS: We identified three novel PV in PITX2 (NM_153427.2:c.217G>A, c.233T>C and c.279del) and two in FOXC1 [NM_001453.2:c.274C>T (novel) and c.454T>A] in five ARS patients. The previously reported FOXC1 c.367C>T or p.(Gln123*) variant was identified in a patient with ASD. The ocular phenotype related to FOXC1 included aniridia, corneal opacity and early onset glaucoma, while an asymmetric ocular phenotype and aniridia were associated with PITX2. No gene rearrangements were documented by MLPA analysis, nor were any PV identified in PAX6 or CYP1B1. CONCLUSIONS: Heterozygous PV in the PITX2 and FOXC1 genes accounted for 66% (6/9) of the ARS/ASD cases. The absence of PAX6 or CYP1B1 abnormalities could reflect our small sample size, although their analysis could be justified in ARS/ASD patients that present with congenital glaucoma or aniridia.

Mutational spectrum of PTS gene and in silico pathological assessment of a novel variant in Mexico.

BACKGROUND: Tetrahydrobiopterin (BH4) is the cofactor for 6-pyruvoyl-tetrahydropterin synthase (PTPS); it is involved in BH4 biosynthesis and is encoded by PTS gene. Its deficiency (PTPSD) is characterized by hyperphenylalaninemia (HPA) and deficit in central monoamine neurotransmitters. We describe the clinical and mutational spectrum of five patients with PTPSD, from four unrelated Mexican families. All patients had symptomatic diagnosis and presented severe early neurological manifestations and HPA. METHODS: Clinical and biochemical data from studied patients were recorded. Responsible PTPSD genotypes was determined by direct and bidirectional Sanger DNA sequencing of the six PTS coding exons and their exon-intron borders, and these were directly searched in the available relatives. The novel PTS missense variant [NM_3000317.2:331G > T, p.(Ala111Ser)] was subjected to in silico, to predict a possible deleterious effect. RESULTS: Diminished fetal movements were perceived as a uniform characteristic in the studied group. DNA sequencing showed two known p.(Arg25∗) and p.(Val132TyrFs∗19) and the novel missense p.(Ala111Ser) PTS variants, the latter representing potentially a frequent PTPSD-responsible allele (50%, 4/8) in Mexican patients. In silico protein modeling analysis of the p.(Ala111Ser) variant revealed loss of hydrophobic interactions between the alanine and neighboring valines, suggesting that these changes in polarity may be detrimental for enzyme function, structure and/or stability. CONCLUSIONS: This work contributes to the knowledge of PTPS molecular spectrum. The delayed diagnosis of these patients emphasizes the importance of considering BH4 metabolism defects in the differential diagnosis of HPA, especially for countries that are beginning their HPA newborn screening programs.

Newborn cystic fibrosis screening in southeastern Mexico: Birth prevalence and novel CFTR gene variants.

OBJECTIVE: To use the results of the first five years of a cystic fibrosis newborn screening program to estimate the cystic fibrosis birth prevalence and spectrum of cystic fibrosis transmembrane conductance regulator ( CFTR) gene variants in Yucatan, Mexico. METHODS: Screening was performed from 2010 to 2015, using two-tier immunoreactive trypsinogen testing, followed by a sweat test. When sweat test values were >30 mmol/L, the CFTR gene was analyzed. RESULTS: Of 96,071 newborns screened, a second sample was requested in 119 cases. A sweat test was performed in 30 newborns, and 9 possible cases were detected (seven confirmed cystic fibrosis and two inconclusive). The most frequently detected CFTR pathogenic variant (5/14 cystic fibrosis alleles, 35.7%) was p.(Phe508del); novel p.(Ala559Pro) and p.(Thr1299Hisfs*29) pathogenic variants were found. CONCLUSIONS: Cystic fibrosis birth prevalence in southeastern Mexico is 1:13,724 newborns. Immunoreactive trypsinogen blood concentration is influenced by gestational age and by the time of sampling. The spectrum of CFTR gene variants in Yucatan is heterogeneous.

Unique association of hypochondroplasia with craniosynostosis and cleft palate in a Mexican family.

Hypochondroplasia (HCH) is a skeletal dysplasia caused by an abnormal function of the fibroblast growth factor receptor 3. Although believed to be relatively common, its prevalence and phenotype are not well established owing to its clinical, radiological, and genetic heterogeneity. Here we report on a molecularly proven HCH family with an affected father and two children. The siblings (male and female) with HCH also had craniosynostosis and cleft palate, respectively. The present report supports the conclusion that the full clinical spectrum of HCH is not completely delineated. It also suggests that secondary, as yet unknown, modifying factors can influence the final phenotype.