New Noncoding Base Pair Mutation at the Identical Locus as the Original NCMD/MCDR1 in a Mexican Family, Suggesting a Mutational Hotspot.

Purpose: To clinically and molecularly study a newly found family with North Carolina macular dystrophy (NCMD/MCDR1) from Mexico. Methods: This retrospective study comprised 6 members of a 3-generation Mexican family with NCMD. Clinical ophthalmic examinations, including fundus imaging, spectral-domain optical coherence tomography, electroretinography, and electrooculography, were performed. Genotyping with polymorphic markers in the MCDR1 region was performed to determine haplotypes. Whole-genome sequencing (WGS) was performed followed by variant filtering and copy number variant analysis. Results: Four subjects from 3 generations were found to have macular abnormalities. The proband presented with lifelong bilateral vision impairment with bilaterally symmetric vitelliform Best disease-like appearing macular lesions. Her 2 children had bilateral large macular coloboma-like malformations, consistent with autosomal dominant NCMD. The 80-year-old mother of the proband had drusen-like lesions consistent with grade 1 NCMD. WGS and subsequent Sanger sequencing found a point mutation at chr6:99593030G>C (hg38) in the noncoding region of the DNase I site thought to be a regulatory element of the retinal transcription factor gene PRDM13. This mutation is the identical site/nucleotide as in the original NCMD family (#765) but is a guanine to cytosine change rather than a guanine to thymine mutation, as found in the original NCMD family. Conclusions: We report a new noncoding mutation at the same locus (chr6:99593030G>C) involving the same DNase I site regulating the retinal transcription factor gene PRDM13. This suggests that this site, chr6:99593030, is a mutational hotspot.

Síndrome de deleção 6q: relato de caso de um achado raro no Amazonas, Brasil / Deletion 6q syndrome: case report of a rare finding in Amazonas, Brazil

Objetivos: Síndrome da deleção 6q é considerada uma anomalia cromossômica rara. Assim, nosso objetivo foi relatar um caso de um menino com essa síndrome, em Manaus/Amazonas. Descrição do caso: Menino com quatro anos de idade que apresenta atraso do crescimento e do desenvolvimento neuropsicomotor, dificuldades de ganho de peso e anormalidades na retina. A análise citogenética do paciente revelou cariótipo com 46, XY, del(6)(q25-qter). Conclusões: Este relato demonstrou a importância das análises citogenéticas para o diagnóstico preciso das anomalias congênitas, pois auxiliam no encaminhamento de tratamentos adequados aos pacientes e na ampliação de conhecimento científico relacionado a essa deleção.

Aims: Deletion 6q syndrome is considered a rare chromosomal anomaly. Thus, our objective was to report a rare case of a boy with 6q deletion syndrome. Case description: 4-year-old boy with delayed growth and neuropsychomotor development, weight gain difficulties and retinal abnormalities. Karyotypic analysis of the patient revealed karyotype 46, XY, del (6) (q25-qter). That is, a deletion in the long arm of one of the chromosome 6, specifically in the distal region of the long arm of the 6q25 band up to the 6qter band. Conclusions: This report demonstrates the importance of cytogenetic analyzes for the accurate diagnosis of congenital anomalies, as they assist in referring appropriate treatments to patients and in expanding scientific knowledge related to this deletion.

Ring chromosome 6 in a child with anterior segment dysgenesis and review of its overlap with other FOXC1 deletion phenotypes.

Here, we report a patient with ring chromosome 6 [r(6)], associated with anterior segment dysgenesis (ASD) and other anomalies. The phenotype was due to a 1880 kb microdeletion at 6p25.3 identified by whole-genome array analysis, and was mainly attributable to a FOXC1 haploinsufficiency. Currently 37 patients with r(6) have been reported. We found that facial dysmorphism, ASD, heart anomalies, brain anomalies, and hearing loss are constant features only in severe cases of r(6), mainly related to hemizygosity of FOXC1. Thus, overlaps with other FOXC1 related phenotypes, such as the 6p25 deletion syndrome, Axenfeld-Rieger syndrome type 3, and ASD type 3. Contrarily, those patients whose r(6) does not disrupt FOXC1, have mild or moderate phenotypes and do not exhibit ASD.

Investigation of major genetic alterations in neuroblastoma.

Neuroblastoma (NB) is the most common extracranial solid tumor in childhood. This malignancy shows a wide spectrum of clinical outcome and its prognosis is conditioned by manifold biological and genetic factors. We investigated the tumor genetic profile and clinical data of 29 patients with NB by multiplex ligation-dependent probe amplification (MLPA) to assess therapeutic risk. In 18 of these tumors, MYCN status was assessed by fluorescence in situ hybridization (FISH). Copy number variation was also determined for confirming MLPA findings in two 6p loci. We found 2p, 7q and 17q gains, and 1p and 11q losses as the most frequent chromosome alterations in this cohort. FISH confirmed all cases of MYCN amplification detected by MLPA. In view of unexpected 6p imbalance, copy number variation of two 6p loci was assessed for validating MLPA findings. Based on clinical data and genetic profiles, patients were stratified in pretreatment risk groups according to international consensus. MLPA proved to be effective for detecting multiple genetic alterations in all chromosome regions as requested by the International Neuroblastoma Risk Group (INRG) for therapeutic stratification. Moreover, this technique proved to be cost effective, reliable, only requiring standard PCR equipment, and attractive for routine analysis. However, the observed 6p imbalances made PKHD1 and DCDC2 inadequate for control loci. This must be considered when designing commercial MLPA kits for NB. Finally, four patients showed a normal MLPA profile, suggesting that NB might have a more complex genetic pattern than the one assessed by presently available MLPA kits.

Un caso de deleción parcial 1p36. 1 y trisomía parcial 6p diagnosticadas por cariotipo / A case of partial 1p36. 1 deletion and partial trisomy 6p diagnosed by karyotype

La deleción de la región cromosómica 1p36 es una de las anomalías subteloméricas más frecuentes y causa rasgos dismórficos distintivos. Por otro lado, la trisomía distal del brazo corto del cromosoma 6 es una anormalidad cromosómica poco frecuente de fenotipo variable. Objetivo: Presentar el caso de un paciente con ambas alteraciones cromosómicas, y resaltar la vigencia e importancia del cariotipo como herramienta diagnóstica en dismorfología. Caso clínico: Lactante de 2 meses de edad con múltiples anomalías craneofaciales, hemangioma en la nuca, fosita sacra, acortamiento rizomélico, pies y manos pequeños, criptorquidia unilateral izquierda e hipotonía. Además, antecedente de restricción del crecimiento intrauterino. Producto del octavo embarazo de una mujer G8A7C1 de 28 años. Con estos hallazgos inespecíficos en el fenotipo se solicitó cariotipo que mostró una deleción parcial de 1p36.1 y una trisomía parcial de cromosoma 6p. Conclusión: El cariotipo convencional sigue siendo una herramienta importante para el etiológico en pacientes con anomalías congénitas (múltiples), mostrando en este caso una deleción parcial de 1p36.1 y una trisomía parcial de cromosoma 6p, alteraciones cromosómicas estructurales.

The deletion of chromosomal region 1p36 is one of the most common sub-telomeric microdeletion syndromes and has distinctive dysmorphic features. On the other hand, partial trisomy of the short arm of chromosome 6 is a rare chromosomal abnormality with a variable phenotype. Objective: To report a case with both chromosome abnormalities, and to highlight the importance of the karyotype as a diagnostic tool in dysmorphology. Clinical case: The case of is presented of a two month-old infant with several craniofacial anomalies, neck haemangioma, sacral pit, rhizomelic shortening, small hands and feet, left unilateral cryptorchidism, and hypotonia. The infant also suffered intrauterine growth restriction and is the product of the eighth pregnancy of a 28 years old woman. Due to the unspecific findings in phenotype, a karyotype was requested, which showed a partial deletion of 1p36.1 and a partial trisomy of chromosome 6. Conclusion: The development of new techniques in molecular biology has improved diagnostic possibilities in medical genetics. However, the traditional karyotype remains as an important diagnostic tool in patients with multiple congenital anomalies.

[A case of partial 1p36.1 deletion and partial trisomy 6p diagnosed by karyotype]. / Un caso de deleción parcial 1p36.1 y trisomía parcial 6p diagnosticadas por cariotipo.

The deletion of chromosomal region 1p36 is one of the most common sub-telomeric microdeletion syndromes and has distinctive dysmorphic features. On the other hand, partial trisomy of the short arm of chromosome 6 is a rare chromosomal abnormality with a variable phenotype. OBJECTIVE: To report a case with both chromosome abnormalities, and to highlight the importance of the karyotype as a diagnostic tool in dysmorphology. CLINICAL CASE: The case of is presented of a two month-old infant with several craniofacial anomalies, neck haemangioma, sacral pit, rhizomelic shortening, small hands and feet, left unilateral cryptorchidism, and hypotonia. The infant also suffered intrauterine growth restriction and is the product of the eighth pregnancy of a 28 years old woman. Due to the unspecific findings in phenotype, a karyotype was requested, which showed a partial deletion of 1p36.1 and a partial trisomy of chromosome 6. CONCLUSION: The development of new techniques in molecular biology has improved diagnostic possibilities in medical genetics. However, the traditional karyotype remains as an important diagnostic tool in patients with multiple congenital anomalies.

Recognition deficits in mice carrying mutations of genes encoding BLOC-1 subunits pallidin or dysbindin.

Numerous studies have implicated DTNBP1, the gene encoding dystrobrevin-binding protein or dysbindin, as a candidate risk gene for schizophrenia, though this relationship remains somewhat controversial. Variation in dysbindin, and its location on chromosome 6p, has been associated with cognitive processes, including those relying on a complex system of glutamatergic and dopaminergic interactions. Dysbindin is one of the seven protein subunits that comprise the biogenesis of lysosome-related organelles complex 1 (BLOC-1). Dysbindin protein levels are lower in mice with null mutations in pallidin, another gene in the BLOC-1, and pallidin levels are lower in mice with null mutations in the dysbindin gene, suggesting that multiple subunit proteins must be present to form a functional oligomeric complex. Furthermore, pallidin and dysbindin have similar distribution patterns in a mouse and human brain. Here, we investigated whether the apparent correspondence of pallid and dysbindin at the level of gene expression is also found at the level of behavior. Hypothesizing a mutation leading to underexpression of either of these proteins should show similar phenotypic effects, we studied recognition memory in both strains using the novel object recognition task (NORT) and social novelty recognition task (SNRT). We found that mice with a null mutation in either gene are impaired on SNRT and NORT when compared with wild-type controls. These results support the conclusion that deficits consistent with recognition memory impairment, a cognitive function that is impaired in schizophrenia, result from either pallidin or dysbindin mutations, possibly through degradation of BLOC-1 expression and/or function.

Cytogenomic delineation and clinical follow-up of two siblings with an 8.5 Mb 6q24.2-q25.2 deletion inherited from a paternal insertion.

The chromosomal segment 6q24-q25 comprises a contiguous gene microdeletion syndrome characterized by intrauterine growth retardation, growth delay, intellectual disability, cardiac anomalies, and a dysmorphic facial phenotype. We describe here a 10-year follow-up with detailed clinical, neuropsychological, and cytomolecular data of two siblings, male and female, who presented with developmental delay, microcephaly, short stature, characteristic facial dysmorphisms, multiple organ anomalies, and intellectual disability. Microarray analysis showed an 8.5 Mb 6q24.2-q25.2 interstitial deletion. Fluorescence in situ hybridization analyses confirmed the deletions and identified an insertion of 6q into 8q13 in their father, resulting in a high recurrence risk. This is the first report in sibs with distinct neuropsychological involvement, one of them with stenosis of the descending branch of the aorta.