Investigating Chromosomal Radiosensitivity in Inborn Errors of Immunity: Insights from DNA Repair Disorders and Beyond

Abstract

Human inborn errors of immunity (IEI) represent a diverse group of genetic disorders affecting the innate and/or adaptive immune system. Some IEI entities comprise defects in DNA repair factors, resulting in (severe) combined immunodeficiencies, bone marrow failure, predisposition to malignancies, and potentially resulting in radiosensitivity (RS). While other IEI subcategories such as common variable immunodeficiency (CVID) and immune dysregulation disorders also associate with lymphoproliferative and malignant complications, the occurrence of RS phenotypes in the broader IEI population is not well characterized. Nonetheless, identifying RS in IEI patients through functional testing is crucial to reconsider radiation-related therapeutic protocols and to improve overall patient management. This study aimed to investigate chromosomal RS in a diverse cohort of 107 IEI patients using the G0 cytokinesis-block micronucleus (MN) assay. Our findings indicate significant variability in RS across specific genetic and phenotypical subgroups. Severe RS was detected in all ataxia-telangiectasia (AT) patients, a FANCI deficient and ERCC6L2 deficient patient, but not in any other IEI patient included in this cohort. Age emerged as an influencing factor for both spontaneous and radiation-induced MN yields, while the manifestation of additional clinical features, including infection susceptibility, immune dysregulation, or malignancies did not associate with increased MN levels. Our extensive analysis of RS in the IEI population underscores the clinical importance of RS assessment in AT patients and supports RS testing in all IEI patients suspected of having a DNA repair disorder associated with RS.

Keywords: DNA repair; Human Inborn Errors of Immunity (IEI); Micronucleus assay; Radiosensitivity.

Fig. 1

Evaluation of chromosomal instability and radiosensitivity (RS) of the entire IEI patient cohort. Results of G0 MN assay on fresh blood samples, analyzed after 70 h of culture. a Spontaneous (0 Gy) and radiation-induced (1 Gy) MN yields are displayed per IUIS subgroup for all patients. Chromosomal instability was indicated when MN values exceed the mean + 3SD threshold (dashed line) for 0 Gy. Patients with radiation-induced MN yields (1 Gy) higher than the mean + 2SD threshold (dotted line) or higher than the mean + 3SD threshold (dashed line) were classified as intermediate or severe radiosensitive, respectively. Patients were considered not radiosensitive when the MN yields were lower than the mean + 2SD threshold. b Reproducibility of the G0 MN assay was assessed by comparing spontaneous (0 Gy) and radiation-induced (1 Gy) MN yields of the first and second sampling for 11 healthy controls, 3 heterozygous carriers, and 12 patients. Patients that exceeded the 0 Gy and/or 1 Gy threshold are annotated on both panels

Fig. 2

Chromosomal instability and radiosensitivity phenotypes according to specific gene defects. Results of G0 MN assay on fresh blood samples, analyzed after 70 h of culture. Spontaneous (0 Gy) and radiation-induced MN yields (1 Gy) are shown for healthy controls (HCs), heterozygous mutation carriers and patients with a confirmed genetic diagnosis, displayed per IUIS group. a Patients with a confirmed genetic defect in IUIS group I (immunodeficiencies affecting cellular and humoral immunity) (b) Patients with an identified defect in IUIS group II (combined immunodeficiency (CID) with associated or syndromic features). c Variability in MN results (0 Gy, 0.5 Gy, and 1 Gy) among the 9 ataxia telangiectasia (AT) patients, distinguished according to the mutation type. Four patients carried two truncating variants, one harbored a biallelic missense variant, and 4 were compound heterozygous for a truncating and a non-truncating variant. Symbols with the same shape and color across doses represent the same AT patient. d Relatives of IEI patients carrying a heterozygous mutation in ATM or DCLRE1C (Artemis). e Patients classified in group III (predominantly antibody deficiencies), displayed separately for common variable immunodeficiency (CVID) and non-CVID (other) patients. f Patients with a confirmed genetic defect in IUIS group IV (diseases of immune dysregulation), group V (congenital defects in phagocyte number and function) or group VI (defects in intrinsic and innate immunity). g Patients in IUIS group IX (bone marrow failure), according to their genetic defect or subcategory: severe aplastic anemia (SAA), myelodysplastic syndrome (MDS) or undefined. Dotted and dashed lines indicate the mean + 2SD and mean + 3SD threshold values, respectively

Fig. 3

The occurrence of IEI-related co-morbidities are not associated with increased spontaneous or radiation-induced MN frequencies. Results of G0 MN assay on fresh blood samples, analyzed after 70 h of culture. Association between MN yields and the following clinical features and immunological manifestations were investigated: a sex, b age at inclusion, c recurrent infections, d lymphoproliferation, e autoimmunity, and (f) history of malignancy. Spontaneous (0 Gy) and radiation-induced MN yields (1 Gy) are displayed for each parameter. Boxplots depict the median, lower and upper quartiles of the MN yields, whiskers indicate minimum and maximum values. Statistical significance was assessed using the Mann–Whitney test (0 Gy) or unpaired t-tests (1 Gy). Patients with a confirmed defect in one of the DNA DSB repair-related genes were excluded for this analysis

Fig. 4

Age-related variation in spontaneous and radiation-induced MN yields in the entire cohort of IEI patients, heterozygous carriers, and healthy controls. Results of G0 MN assay on fresh blood samples, analyzed after 70 h of culture. A correlation analysis was performed between age and (a) spontaneous (0 Gy) and (b) radiation-induced MN yields (1 Gy), by calculating the Spearman's rank correlation coefficient (r). The healthy control and IEI patient cohort were analyzed separately, as well as the entire study population together (healthy controls, patients, and heterozygous carriers). Patients with a confirmed defect in one of the DNA DSB repair-related genes were excluded for this analysis