Peripherin gene is linked to keratin 18 gene on human chromosome 12

Pituitary hormones are specifically expressed in trigeminal sensory neurons and contribute to pain responses in the trigeminal system

Trigeminal (TG), dorsal root (DRG), and nodose/jugular (NG/JG) ganglia each possess specialized and distinct functions. We used RNA sequencing of two-cycle sorted Pirt-positive neurons to identify genes exclusively expressing in L3-L5 DRG, T10-L1 DRG, NG/JG, and TG mouse ganglion neurons. Transcription factor Phox2b and Efcab6 are specifically expressed in NG/JG while Hoxa7 is exclusively present in both T10-L1 and L3-L5 DRG neurons. Cyp2f2, Krt18, and Ptgds, along with pituitary hormone prolactin (Prl), growth hormone (Gh), and proopiomelanocortin (Pomc) encoding genes are almost exclusively in TG neurons. Immunohistochemistry confirmed selective expression of these hormones in TG neurons and dural nerves; and showed GH expression in subsets of TRPV1+ and CGRP+ TG neurons. We next examined GH roles in hypersensitivity in the spinal versus trigeminal systems. Exogenous GH produced mechanical hypersensitivity when injected intrathecally, but not intraplantarly. GH-induced thermal hypersensitivity was not detected in the spinal system. GH dose-dependently generated orofacial and headache-like periorbital mechanical hypersensitivity after administration into masseter muscle and dura, respectively. Periorbital mechanical hypersensitivity was reversed by a GH receptor antagonist, pegvisomant. Overall, pituitary hormone genes are selective for TG versus other ganglia somatotypes; and GH has distinctive functional significance in the trigeminal versus spinal systems.

Desmoplastic and spindle cell melanomas express protein markers of the neural crest but not of later committed stages of Schwann cell differentiation

BACKGROUND

The rare desmoplastic and spindle cell variants of malignant melanoma exhibit histological and biochemical features suggestive of early Schwann cell differentiation. These features include a spindle-shaped morphology, neurotropism, and the expression of the low affinity nerve growth factor receptor (p75NGFR).

METHODS

We evaluated by immunohistochemistry (using formalin-fixed, paraffin-embedded tissues) nine desmoplastic and three spindle cell melanomas for the expression of peripherin, p75NGFR, neural cell adhesion molecule (CD56/N-CAM), and growth-associated phosphoprotein-43 (GAP-43). Peripherin is expressed in the neural crest and in neurons, but not in cells committed to the Schwann cell lineage. p75NGFR and CD56/N-CAM also are expressed in early neural crest cells, but persist in unmyelinated and early premyelinating Schwann cells. GAP-43 is expressed in unmyelinated Schwann cells, but is downregulated in the later premyelinating to promyelinating stages of cells committed to the Schwann cell lineage.

RESULTS

Peripherin was expressed in 7/12 (58%), p75NGFR in 4/12 (33%), and CD56/N-CAM in 6/12 (50%) of the desmoplastic and spindle cell melanomas. GAP-43 was not expressed (0%) in any of the 12 melanomas (chi2, p = 0.05).

CONCLUSIONS

Desmoplastic and spindle cell melanomas express protein markers common to cells of the neural crest and to neurons similar to the immunophenotype previously reported for epithelioid cell melanomas. The expression of peripherin and the lack of expression of GAP-43 further define that these rare subtypes of melanoma do not recapitulate the later committed stages of Schwann cell differentiation.

Immunohistochemistry in diagnostic dermatopathology

This article briefly reviews many immunohistochemical stains that have been in use for years, emphasizing their diagnostic use and potential pitfalls. Several newer immunostains are described in a more comprehensive fashion, including brief summaries from recently published studies.

Differential expression of the intermediate filament peripherin in cutaneous neural lesions and neurotized melanocytic nevi

Peripherin is an intermediate filament involved in growth and development of the peripheral nervous system, and is produced by neurons and the beta cells of the islets of Langerhans. Recently, malignant melanomas and some melanocytic nevi have been shown to express peripherin. It is unknown if Schwann cells, also derived from the neural crest, express peripherin. Expression of peripherin was evaluated by immunohistochemistry in cutaneous lesions characterized by a prominent Schwann cell component including 26 neurofibromas (NF), 10 schwannomas (SCH), seven granular cell tumors, and five palisaded encapsulated neuromas (PEN); 13 neurotized melanocytic nevi (NMN) also were evaluated because these lesions contain Wagner-Meissnerlike structures and type C nevus cells, which exhibit a "schwannian" phenotype. Peripherin was detected in the axons of normal peripheral nerves. NF and PEN contained numerous axons dispersed throughout the lesions, whereas only scattered small nerves were seen in GCT. In SCH, only rare axons were labeled, mostly at the periphery of the lesions. All other cells in these four types of lesions, therefore including Schwann cells, were not labeled. In most NMN, labeled axons were identified within the lesions. In a few cases, rare epithelioid melanocytes within the superficial portions of the nevi were labeled. The Wagner-Meissnerlike structures and type C nevus cells (schwannian) were not labeled in any lesion; however, numerous labeled axons invested these areas. Because there are different relative numbers of peripherin-labeled axons throughout NF, PEN, some nevi, and SCH, analysis of peripherin expression may be helpful in the diagnosis of these lesions. Neurons and some epithelioid melanocytes, in contrast to type C nevus cells and Schwann cells of NF and SCH, express peripherin, providing further evidence for a transition from a more neuronal to a more schwannian phenotype during the normal maturation sequence of melanocytes in nevi.

The intermediate filament peripherin is expressed in cutaneous melanocytic lesions

Peripherin is an intermediate filament involved in growth and development of the peripheral nervous system and is localized to neurons, some other cells derived from neural tube and neural crest, and some neuroendocrine cells (e.g. beta cells of islets of Langerhans). Peripherin also has been demonstrated in neuroblastomas and cutaneous neuroendocrine (Merkel cell) carcinomas. The expression of peripherin by other cells derived from the neural crest is unknown. We evaluated by immunohistochemistry 74 cutaneous melanocytic lesions including primary invasive malignant melanoma (IMM), melanoma in situ (MIS), atypical nevus (nevus with architectural disorder and cytologic atypia of melanocytes) (AN), spindle and epithelioid cell nevus (Spitz nevus) (SN), blue nevus (BN), and common intradermal benign melanocytic nevus (BMN) for expression of peripherin. Peripherin was detected in a cytoplasmic distribution within tumor cells in 14/14 IMM and 8/10 MIS. For IMM, peripherin localized to both the intraepidermal and invasive dermal components. Peripherin was detected in 10/10 AN and 9/9 SN, being localized to the intraepidermal component and, focally, to the superficial dermal component of the lesions. The dendritic nevus cells in 15/15 BN also expressed peripherin. For most of the BMN, expression of peripherin was absent or limited to rare, scattered cells in the superficial portion of the lesions. Melanocytes in adjacent normal skin were not labeled in any of the lesions studied. These results indicate that expression of peripherin is common in both benign and malignant melanocytic lesions, but not in normal resting adult melanocytes. Among benign lesions, expression of peripherin in the dermal component is rare except in the dendritic cells of BN. These findings provide evidence that the expression of peripherin, a marker of neuronal differentiation, is maintained by IMM, MIS, and BN, but is lost in the normal maturational sequence of the dermal component of other melanocytic lesions.

Cytogenetic and molecular analysis in trisomy 12p

We studied a male patient with de novo pure trisomy 12p syndrome by molecular analysis and fluorescence in situ hybridization (FISH) with markers from chromosome 12. G-banding studies demonstrated a 46,XY, 22p+ karyotype and the banding pattern and clinical findings suggested that the extra chromosomal material was derived from 12p. Trisomy 12p was confirmed by dosage analysis with chromosome 12p markers and FISH analysis with a whole chromosome 12 paint. The de novo re-arranged chromosome was of paternal origin. A comparison of the clinical and cytogenetic findings in this patient was made with previously described cases of trisomy 12p. We propose a classification system for 12p trisomy in order to better characterize the correlative relationships between specific cytogenetic constitution and phenotype.