Marsilio Adriani

Ancestral Founder Mutation of the Nude (FOXN1) Gene in Congenital Severe Combined Immunodeficiency Associated with Alopecia in Southern Italy Population

Genetic alterations of the FOXN1 transcription factor, selectively expressed in thymic epithelia and skin, are responsible in both mice and humans for the Nude/SCID phenotype. The first described human FOXN1 mutation was a C792T transition in exon 5 resulting in the nonsense mutation R255X, and was detected in two probands originated from a small community in southern Italy. In this community, four additional children affected with congenital alopecia died in early childhood because of severe infections. In this study, we report on the screening for this mutation in 30% of the village population. This analysis led us to identify 55 heterozygous carriers (6.52%) of the R255X mutation out of 843 inhabitants screened. A genealogical study revealed that these subjects, belonging to 39 families, were linked in an extended 7‐generational pedigree comprising 483 individuals. Through the archival database a single ancestral couple, born at the beginning of the 19th century, was identified. To confirm the ancestral origin of the mutation we genotyped two microsatellite markers, D17S2187 and D17S1880, flanking the FOXN1 gene on chromosome 17. The three haplotypes identified, 3/R255X/3, 3/R255X/2 and 3/R255X/1, are consistent with a single ancestral origin for the mutation R255X.

The Cellular Amount of the Common γ-Chain Influences Spontaneous or Induced Cell Proliferation

Mutations of the IL2RG encoding the common γ-chain (γc) lead to the X-linked SCID disease. Gene correction through ex vivo retroviral transduction restored the immunological impairment in the most of treated patients, although lymphoproliferative events occurred in five of them. Even though in two cases it was clearly documented an insertional mutagenesis in LMO2, it is conceivable that γc could have a role per se in malignant lymphoproliferation. The γc is a shared cytokine receptor subunit, involved also in growth hormone (GH) receptor signaling. Through short interfering RNA or using X-linked SCID B lymphoblastoid cell lines lacking γc, we demonstrate that self-sufficient growth was strongly dependent on γc expression. Furthermore, a correlation between γc amount and the extent of constitutive activation of JAK3 was found. The reduction of γc protein expression also reduced GH-induced proliferation and STAT5 nuclear translocation in B lymphoblastoid cell lines. Hence, our data demonstrate that γc plays a remarkable role in either spontaneous or GH-induced cell cycle progression depending on the amount of protein expression, suggesting a potential role as enhancing cofactor in lymphoproliferation.

Functional interaction of common gamma-chain and growth hormone receptor signaling apparatus.

We previously reported on an X-linked SCID (X-SCID) patient, who also had peripheral growth hormone (GH) hyporesponsiveness and abnormalities of the protein phosphorylation events following GH receptor (GHR) stimulation. In the present study, we examined a potential role of common cytokine receptor γ-chain (γc) in GHR signaling using EBV-transformed lymphocytes from healthy subjects and γc-negative X-SCID patients. We demonstrated that the proliferative response to GH stimulation of the B cell lines of γc-negative patients was impaired despite a comparable cellular expression of GHR molecules to controls. In patients, after GH stimulation, no phosphorylation of STAT5 was observed. In addition, the molecule localization through confocal microscopy revealed that in B cell lines of patients no nuclear translocation of STAT5b following GH stimulation occurred differently from controls. Biochemical analysis of the nuclear extracts of γc-negative cell lines provided further evidence that the amount of STAT5b and its phosphorylated form did not increase following GH stimulation. In patients, cells reconstituted with wild-type γc abnormal biochemical and functional events were restored resulting in nuclear translocation of STAT5. Confocal experiments revealed that GHR and γc were colocalized on the cell membrane. Our study demonstrates the existence of a previously unappreciated relationship between GHR-signaling pathway and γc, which is required for the activation of STAT5b in B cell lines. These data also confirm that growth failure in X-SCID is primarily related to the genetic alteration of the IL2RG gene.

Cutaneous manifestations as presenting sign of autoimmune lymphoproliferative syndrome in childhood.

Autoimmune lymphoproliferative syndrome is a disorder due to a defect of lymphocyte apoptosis, whose clinical manifestations consist of hyperplasia of lymphoid tissues and autoimmune diseases. We report on a 26-month-old child who presented with frequent eruptions of weals and angioedema without any apparent triggering factor, who subsequently developed an erythematopapular rash with a histological pattern of a lymphoplasmacellular infiltrate. Familial anamnesis revealed a history of lymphoadenomegaly and massive spleen and liver enlargement in her sister. Functional and molecular analysis led to a diagnosis of type 1a autoimmune lymphoproliferative syndrome. Immunophenotyping of the cutaneous lesion revealed the presence of an inflammatory infiltrate with a considerably high number of Langerhans cells. Cutaneous features such as urticaria, angioedema and vasculitis in children with a personal and familial history of hyperplasia of lymphoid tissues may be a presenting sign of a systemic disease, such as autoimmune lymphoproliferative syndrome.