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Nijmegen breakage syndrome detected by newborn screening for T cell receptor excision circles (TRECs).

Patel JP, Puck JM, Srinivasan R, Brown C, Sunderam U, Kundu K, Brenner SE, Gatti RA, Church JA - J. Clin. Immunol. (2015)

Bottom Line: Immunoblotting showed absence of nibrin protein.A colony survival assay demonstrated radiosensitivity comparable to patients with ataxia telangiectasia.Timely identification of an infant with T lymphopenia allowed for prompt pursuit of underlying etiology, making possible a diagnosis of NBS, genetic counseling, and early intervention to minimize complications.

View Article: PubMed Central - PubMed

Affiliation: Division of General Pediatrics, Children's Hospital of Los Angeles, Los Angeles, CA, USA, jpatel@chla.usc.edu.

ABSTRACT

Purpose: Severe combined immunodeficiency (SCID) encompasses a group of disorders characterized by reduced or absent T-cell number and function and identified by newborn screening utilizing T-cell receptor excision circles (TRECs). This screening has also identified infants with T lymphopenia who lack mutations in typical SCID genes. We report an infant with low TRECs and non-SCID T lymphopenia, who proved upon whole exome sequencing to have Nijmegen breakage syndrome (NBS).

Methods: Exome sequencing of DNA from the infant and his parents was performed. Genomic analysis revealed deleterious variants in the NBN gene. Confirmatory testing included Sanger sequencing and immunoblotting and radiosensitivity testing of patient lymphocytes.

Results: Two novel nonsense mutations in NBN were identified in genomic DNA from the family. Immunoblotting showed absence of nibrin protein. A colony survival assay demonstrated radiosensitivity comparable to patients with ataxia telangiectasia.

Conclusions: Although TREC screening was developed to identify newborns with SCID, it has also identified T lymphopenic disorders that may not otherwise be diagnosed until later in life. Timely identification of an infant with T lymphopenia allowed for prompt pursuit of underlying etiology, making possible a diagnosis of NBS, genetic counseling, and early intervention to minimize complications.

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Related in: MedlinePlus

Colony Survival Assay for AT and NBS B lymphoblastoid cell lines showing that both the AT control cells and those of patient NBS20LA are in the radiosensitive range, as defined by Sun et al. 2002 [12]
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Fig2: Colony Survival Assay for AT and NBS B lymphoblastoid cell lines showing that both the AT control cells and those of patient NBS20LA are in the radiosensitive range, as defined by Sun et al. 2002 [12]

Mentions: An immunoblot showed no detectable nibrin protein in NBS20LA (Fig. 1, penultimate lane). Interestingly, MRE11 and Rad50 protein levels were also reduced; this reflects the instability of the MRE11-Rad50-nibrin (MRN) complex whenever nibrin is absent. Lane 2 contains LCL protein from an AT patient whose cell lines were radiosensitive in Fig. 2. ATM protein was absent in the ATM LCL, but was present in NBS20LA (not shown). All other LCLs in Fig. 1 were from healthy individuals and showed normal amounts of MRN-complex proteins and the loading control, p84. These findings provided functional confirmation that the patient’s NBN variants were both mutations that abrogated protein expression, and that his cells scored as radiosensitive.Fig. 1


Nijmegen breakage syndrome detected by newborn screening for T cell receptor excision circles (TRECs).

Patel JP, Puck JM, Srinivasan R, Brown C, Sunderam U, Kundu K, Brenner SE, Gatti RA, Church JA - J. Clin. Immunol. (2015)

Colony Survival Assay for AT and NBS B lymphoblastoid cell lines showing that both the AT control cells and those of patient NBS20LA are in the radiosensitive range, as defined by Sun et al. 2002 [12]
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4352190&req=5

Fig2: Colony Survival Assay for AT and NBS B lymphoblastoid cell lines showing that both the AT control cells and those of patient NBS20LA are in the radiosensitive range, as defined by Sun et al. 2002 [12]
Mentions: An immunoblot showed no detectable nibrin protein in NBS20LA (Fig. 1, penultimate lane). Interestingly, MRE11 and Rad50 protein levels were also reduced; this reflects the instability of the MRE11-Rad50-nibrin (MRN) complex whenever nibrin is absent. Lane 2 contains LCL protein from an AT patient whose cell lines were radiosensitive in Fig. 2. ATM protein was absent in the ATM LCL, but was present in NBS20LA (not shown). All other LCLs in Fig. 1 were from healthy individuals and showed normal amounts of MRN-complex proteins and the loading control, p84. These findings provided functional confirmation that the patient’s NBN variants were both mutations that abrogated protein expression, and that his cells scored as radiosensitive.Fig. 1

Bottom Line: Immunoblotting showed absence of nibrin protein.A colony survival assay demonstrated radiosensitivity comparable to patients with ataxia telangiectasia.Timely identification of an infant with T lymphopenia allowed for prompt pursuit of underlying etiology, making possible a diagnosis of NBS, genetic counseling, and early intervention to minimize complications.

View Article: PubMed Central - PubMed

Affiliation: Division of General Pediatrics, Children's Hospital of Los Angeles, Los Angeles, CA, USA, jpatel@chla.usc.edu.

ABSTRACT

Purpose: Severe combined immunodeficiency (SCID) encompasses a group of disorders characterized by reduced or absent T-cell number and function and identified by newborn screening utilizing T-cell receptor excision circles (TRECs). This screening has also identified infants with T lymphopenia who lack mutations in typical SCID genes. We report an infant with low TRECs and non-SCID T lymphopenia, who proved upon whole exome sequencing to have Nijmegen breakage syndrome (NBS).

Methods: Exome sequencing of DNA from the infant and his parents was performed. Genomic analysis revealed deleterious variants in the NBN gene. Confirmatory testing included Sanger sequencing and immunoblotting and radiosensitivity testing of patient lymphocytes.

Results: Two novel nonsense mutations in NBN were identified in genomic DNA from the family. Immunoblotting showed absence of nibrin protein. A colony survival assay demonstrated radiosensitivity comparable to patients with ataxia telangiectasia.

Conclusions: Although TREC screening was developed to identify newborns with SCID, it has also identified T lymphopenic disorders that may not otherwise be diagnosed until later in life. Timely identification of an infant with T lymphopenia allowed for prompt pursuit of underlying etiology, making possible a diagnosis of NBS, genetic counseling, and early intervention to minimize complications.

Show MeSH
Related in: MedlinePlus