The cutis laxa syndromes are multisystem disorders that share loose redundant inelastic and wrinkled skin as a common hallmark clinical feature. The underlying molecular defects are heterogeneous and 13 different genes have been involved until now, all of them being implicated in elastic fiber assembly. We provide here molecular and clinical characterization of three unrelated patients with a very rare phenotype associating cutis laxa, facial dysmorphism, severe growth retardation, hyperostotic skeletal dysplasia, and intellectual disability. This disorder called Lenz–Majewski syndrome (LMS) is associated with gain of function mutations in PTDSS1, encoding an enzyme involved in phospholipid biosynthesis. This report illustrates that LMS is an unequivocal cutis laxa syndrome and expands the clinical and molecular spectrum of this group of disorders. In the neonatal period, brachydactyly and facial dysmorphism are two early distinctive signs, later followed by intellectual disability and hyperostotic skeletal dysplasia with severe dwarfism allowing differentiation of this condition from other cutis laxa phenotypes. Further studies are needed to understand the link between PTDSS1 and extra cellular matrix assembly.

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Neutrophil granulocyte play pivotal roles in inflammatory responses, immune defence, tissue remodeling, and cancer control. Studying rare patients with defects in differentiation and/or function of neutrophil granulocytes highlights genes and pathways orchestrating these important cellular functions. A previously not appreciated role of the signal recognition particle (SRP) has emerged when monoallelic mutations in SRP54 were associated with congenital neutropenia and pancreatic insufficiency. The eukaryotic SRP is composed of six distinct polypeptides (SRP9, SRP14, SRP19, SRP54, SRP68, SRP72) bound to an RNA molecule (the 7SL RNA). SRP and its receptor (SRPRA and SRPRB) cooperatively transport nascent proteins emerging from ribosome to the endoplasmic reticulum (ER) lumen via a protein-conducting channel. We hypothesized that other constituents of the SRP may be involved in the pathophysiology of congenital neutropenia and that disturbances of the SRP may result in defective proteostasis in neutrophil granulocytes. By virtue of our international Care-for-Rare Alliance we identified three kindred with molecularly unsolved congenital neutropenia. Exome-sequencing revealed a de novo monoallelic mutation in SRPRA in one individual in one family and a homozygous splice-site mutation in SRP19 in five individuals from two families. Clinically, all patients with mutations in SRPRA and SRP19 suffered from various degrees of neutropenia and susceptibility to bacterial infections. Pancreatic insufficiency was only seen in patients with mutation in SRPRA, whereas SRP19 deficiency was not associated with any non-hematopoietic symptoms. To functionally validate these novel genetic variants, we set up an in-vitro neutrophil differentiation system allowing us to model the genetic defects in human SRP complex subunits. We introduced patient-specific mutations (SRPRA Q464E and SRP19 c.189+5G>A) into wildtype iPS cells using CRISPR-Cas9 editing. The engineered cells were differentiated into bona fide neutrophil granulocytes. In vitro generated wildtype neutrophil granulocytes had a high degree of resemblance to primary peripheral blood neutrophil granulocytes, as evidenced by phenotypic (light microscopy, cell surface markers, gene expression) and functional (phagocytosis, bacterial killing, rolling and adhesion, chemotaxis) characteristics. In striking contrast to wildtype iPS cells, both SRPRA and SRP19 mutated iPS cells had a significantly reduced capacity to differentiate into neutrophil granulocytes, as shown by colony-forming unit assays and phenotypic analysis. Furthermore, in vitro generated neutrophil granulocytes had higher susceptibility to apoptosis and evidence of increased unfolded protein responses. We went on to characterize the proteome of primary neutrophil granulocytes from patients with SRP-defects by data-independent proteomics technology. Interestingly, neutrophil granulocytes with defects in SRP constituents shared a significantly reduced abundance of the proteins Pentraxin-3 (PTX3) and Glucuronidase Beta (GUSB). These findings were confirmed in both non-hematopoietic HELA cells and promyelocytic HL60 leukemia cells engineered to express the respective SRP mutants. Upon genetic reconstitution, the aberrant protein expression was re-established. In summary, our studies define novel genetic defects causing congenital neutropenia and highlight the relevance of coordinated protein trafficking pathways and homeostasis for physiological differentiation and function of human neutrophil granulocytes. Disclosures No relevant conflicts of interest to declare.

Context. Diabetes mellitus is the most frequent chronic complication in pregnancy and continues to contribute to increased perinatal morbidity and mortality in newborns. Macrosomia, respiratory distress syndrome, metabolic and electrolytic disturbances, and increased rates of congenital structural defects are well-known neonatal complications associated with maternal diabetes, even if well-controlled. Case report. A macrosomic infant born from an insulin-dependent mother, with uncontrolled diabetes and lack of adequate prenatal care, prenatally diagnosed with hydrocephaly showed a complicated postnatal course. Initial respiratory distress syndrome and transient hypoglycemia, rapidly corrected under treatment, were followed by persistent hypocalcemia and hyperphosphatemia due to hypoparathyroidism and evolving hydrocephaly. Ventriculoperitoneal shunting was followed by resolution of hypocalcemia, but seizures associated with schizencephaly and recurrent respiratory tract infections, aggravated by spondylocostal dysplasia, concurred to infant's demise at the age of 5 months. Conclusions. The reported case is rare due to multiple aspects: persistent hypoparathyroidism, uncommon association of schizencephaly, and even rarely association with spondylocostal dysplasia, all these conditions requiring a multidisciplinary therapeutic approach. Also, the reported case is evocative for challenges associated with infants born from diabetic mothers.