The Say-Barber-Biesecker-Young-Simpson variant of Ohdo syndrome (SBBYSS) (MIM# 603736) and genitopatellar syndrome (GPS) (MIM#606170) are allelic diseases caused by KAT6B mutation.
We detected a de novo truncating variant within exon 7 of KAT6B in a 8-year-old female who presented with mild intellectual disability, facial dysmorphisms highly consistent with SBBYSS, and skeletal anomalies including exostosis, that are usually considered component manifestations of GPS.
Using an exome-sequencing approach, we identified de novo mutations of KAT6B in five individuals with GPS; a single nonsense variant and three frameshift indels, including a 4 bp deletion observed in two cases.
KAT6B sequence variants have been identified previously in both patients with the Say-Barber-Biesecker type of blepharophimosis mental retardation syndromes (SBBS) and in the more severe genitopatellar syndrome (GPS).
We suggest that mutations in mid-exon 18 corresponding to the C-terminal end of the acidic (Asp/Glu-rich) domain of KAT6B may have more variable expressivity leading to GPS, SBBYSS or combined phenotypes, in contrast to defects in other regions of the gene which contribute more specifically to either GPS or SBBYSS.
The phenotypic spectrum of KAT6B mutations has been expanding since identification of KAT6B mutations in genitopatellar syndrome (GPS) and Say Barber Biesecker Young Simpson (SBBYS) syndrome patients.
Marked emperipolesis, specific defect of MK alpha-granule content and defect of PAR1-mediated platelet responses are present in all GPS patients that we could study in detail.
It also better characterizes the pathogenesis of defective platelet responses to thrombin, and raises interesting questions on the correlation between abnormal PAR function and the lack of alpha-granule content in GPS.
For the assessment of systemic inflammatory response using the GPS, patients were classified into three groups: Patients with normal serum albumin (<3.5 g/dl) and normal serum C-reactive protein (CRP) (≤1.0 mg/dl) were classified as GPS 0 (n=76), those with low serum albumin (<3.5 g/dl) or elevated serum CRP (>1.0 mg/dl) were classified as GPS 1 (n=58), and those with low serum albumin (<3.5 g/dl) and elevated serum CRP (>1.0 mg/dl) were classified as GPS 2 (n=10).
The diagnostic algorithm recognized: 4 homozygous and 4 heterozygous Bernard-Soulier syndromes, 11 MYH9-related diseases, one von WillebrandOs disease type 2B, one gray platelet syndrome and one X-linked thrombocytopenia with thalassemia.
In addition, GPS treatment markedly suppressed the expression of phosphorylated (p)-ERK, nuclear factor (NF)-κB p65 and cyclin D1, and increased the synthesis of p-P38 and p-JNK protein expression, as evidenced by immunofluorescence and western blotting analyses.
In addition, GPS treatment markedly suppressed the expression of phosphorylated (p)-ERK, nuclear factor (NF)-κB p65 and cyclin D1, and increased the synthesis of p-P38 and p-JNK protein expression, as evidenced by immunofluorescence and western blotting analyses.
This prompted reanalysis of the 5'-untranslated structure of the human RABGGTA gene in normal individuals and in patients with deficiencies of platelet-dense granules (alphadelta-SPD), alpha granules (alpha-SPD or gray platelet syndrome, GPS) or alpha plus dense granules (alphadelta-SPD).
Reduced immunolabeling for platelet factor 4 together with normal immunolabeling for CD63 in MKs of two patients demonstrated that GPS MKs display an alpha granule-specific defect.
This suggests that the locus 9q33-9q34 can be excluded for GPS and that the presented case is unique in its combination of GPS and NPS features caused by a microdeletion associated with loss of function of LMX1B and NR5A1.
In this study, we found that GPS significantly reversed the downregulation of TGR5 and inhibited the overproduction of fibronectin (FN), transforming growth factor β1 (TGF-β1), intercellular adhesion molecule-1 (ICAM-1) and vascular adhesion molecule-1 (VCAM-1) in glomerular mesangial cells (GMCs) exposed to high glucose (HG).
Reduced immunolabeling for platelet factor 4 together with normal immunolabeling for CD63 in MKs of two patients demonstrated that GPS MKs display an alpha granule-specific defect.
In addition, GPS treatment markedly suppressed the expression of phosphorylated (p)-ERK, nuclear factor (NF)-κB p65 and cyclin D1, and increased the synthesis of p-P38 and p-JNK protein expression, as evidenced by immunofluorescence and western blotting analyses.
In addition, GPS treatment markedly suppressed the expression of phosphorylated (p)-ERK, nuclear factor (NF)-κB p65 and cyclin D1, and increased the synthesis of p-P38 and p-JNK protein expression, as evidenced by immunofluorescence and western blotting analyses.
Apart from platelet α-granule deficiency and reduced neutrophil granularity, also monocyte granularity was reduced in Nbeal2<sup>-/-</sup> mice, whereas plasma levels of MPO (myeloperoxidase), elastase, NGAL (neutrophil gelatinase-associated lipocalin), and MMP-9 (matrix metalloproteinase 9), and leukocyte CD11b expression were increased.
Marked emperipolesis, specific defect of MK alpha-granule content and defect of PAR1-mediated platelet responses are present in all GPS patients that we could study in detail.